avformat/rtmpproto: fix memleak when open rtmp failed

Signed-off-by: Steven Liu <lq@chinaffmpeg.org>

libavformat/rtmpproto.c

@@ -2880,6 +2880,9 @@ reconnect:
     return 0;
 
 fail:
+    av_freep(&rt->playpath);
+    av_freep(&rt->tcurl);
+    av_freep(&rt->flashver);
     av_dict_free(opts);
     rtmp_close(s);
     return ret;