obs-outputs: Always call RTMP_Init before connecting

Clears/reinitializes RTMP structure to defaults, preventing data from
potentially persisting between different connections.

Closes jp9000/obs-studio#878

plugins/obs-outputs/rtmp-stream.c

@@ -718,7 +718,7 @@ static int try_connect(struct rtmp_stream *stream)
 
 	info("Connecting to RTMP URL %s...", stream->path.array);
 
-	memset(&stream->rtmp.Link, 0, sizeof(stream->rtmp.Link));
+	RTMP_Init(&stream->rtmp);
 	if (!RTMP_SetupURL(&stream->rtmp, stream->path.array))
 		return OBS_OUTPUT_BAD_PATH;