MT#63171 StatsUDPServer: facilitate shutdown

Wake up thread from blocking on recvfrom() so that it can shut down when
requested to.

Change-Id: Iaa05caf93877363c162d56791a6e24bdfb809094
(cherry picked from commit 392cd9d759)
(cherry picked from commit f15c39899a)

core/plug-in/stats/StatsUDPServer.cpp

@@ -233,6 +233,12 @@ void StatsUDPServer::run()
     
 }
 
+void StatsUDPServer::on_stop()
+{
+  if (sd != -1)
+    shutdown(sd, SHUT_RD);
+}
+
 static int msg_get_line(char*& msg_c, char* str, size_t len)
 {
   size_t l;

core/plug-in/stats/StatsUDPServer.h

@@ -55,7 +55,7 @@ class StatsUDPServer: public AmThread
 		 const struct sockaddr_in& reply_addr);
 	
   void run();
-  void on_stop(){}
+  void on_stop();
 
 public:
   static StatsUDPServer* instance();