net: add a lock around hSocket

src/net.h

@@ -572,6 +572,7 @@ public:
     uint64_t nSendBytes;
     std::deque<std::vector<unsigned char>> vSendMsg;
     CCriticalSection cs_vSend;
+    CCriticalSection cs_hSocket;
 
     CCriticalSection cs_vProcessMsg;
     std::list<CNetMessage> vProcessMsg;