Return true/false if a waiter was/wasn't notified

The method is used as follows:

  if notify_response_waiter(response)
    # Proceed as if a waiter was notified
  end

Previously the return value would be `nil` whenever the loop broke early
due to a waiter being found. This meant that the dispatcher thread often
believed that a packet was not being handled. As a result the
backlog == incomplete sleep kicked in unnecessarily.

Author: joncave

lib/rex/post/meterpreter/packet_dispatcher.rb

@@ -455,15 +455,16 @@ def add_response_waiter(request, completion_routine = nil, completion_param = ni
   # if anyone.
   #
   def notify_response_waiter(response)
+    handled = false
     self.waiters.each() { |waiter|
       if (waiter.waiting_for?(response))
         waiter.notify(response)
-
         remove_response_waiter(waiter)
-
+        handled = true
         break
       end
     }
+    return handled
   end
 
   #