Pass logger to UDP listener

We were already passing it to the TCP and Unixgram listener, but
somehow left it out of the UDP listener setup.

Fixes #285.

Signed-off-by: Matthias Rampke <mr@soundcloud.com>

main.go

@@ -198,7 +198,7 @@ func main() {
 			}
 		}
 
-		ul := &StatsDUDPListener{conn: uconn, eventHandler: eventQueue}
+		ul := &StatsDUDPListener{conn: uconn, eventHandler: eventQueue, logger: logger}
 		go ul.Listen()
 	}