Add a mutex around groups of send() calls in NetworkClient.cpp to fix corrupt packets due to race conditions. If two network RGBControllers try to send a packet with data at the same time, a race condition could cause data from another thread to send in between the header and data for the active thread, corrupting the data stream.

NetworkClient.h

@@ -102,6 +102,7 @@ private:
     unsigned int    server_protocol_version;
     bool            server_protocol_version_received;
     bool            change_in_progress;
+    std::mutex      send_in_progress;
 
     std::thread *   ConnectionThread;
     std::thread *   ListenThread;