Use the same URI that was registered when we deregister

The original URI is registered as '/foobar/' but is deregistered as
'//foobar/', causing it to never get deregistered. Changing this fixes
unregistration of the service handler for staged payloads, but stageless
doesn't work properly if the URI actually gets deregistered.

Author: Brent Cook

lib/rex/post/meterpreter/packet_dispatcher.rb

@@ -79,7 +79,7 @@ def initialize_passive_dispatcher
 
   def shutdown_passive_dispatcher
     return if not self.passive_service
-    self.passive_service.remove_resource("/" + self.conn_id  + "/")
+    self.passive_service.remove_resource(self.conn_id  + "/")
 
     # If there are no more resources registered on the service, stop it entirely
     if self.passive_service.resources.empty?