GUACAMOLE-377: Do not use threaded WebP encoder given that guac_displ…

…ay will already make use of a worker thread pool.

src/libguac/encode-webp.c

@@ -194,7 +194,7 @@ int guac_webp_write(guac_socket* socket, guac_stream* stream,
     /* Add additional tuning */
     config.lossless = lossless;
     config.quality = quality;
-    config.thread_level = 1; /* Multi threaded */
+    config.thread_level = 0; /* NOT multi-threaded (threading results in unnecessary overhead vs. the worker threads used by guac_display) */
     config.method = 2; /* Compression method (0=fast/larger, 6=slow/smaller) */
 
     /* Validate configuration */