Land rapid7#9639, multi/handler exit on disabled handler

If DisablePayloadHandler is set, abort instead of hanging.

Author: wvu

modules/exploits/multi/handler.rb

@@ -52,6 +52,11 @@ def initialize(info = {})
   end
 
   def exploit
+    if datastore['DisablePayloadHandler']
+      print_error "DisablePayloadHandler is enabled, so there is nothing to do. Exiting!"
+      return
+    end
+
     stime = Time.now.to_f
     timeout = datastore['ListenerTimeout'].to_i
     loop do