librtmp: Avoid an infiniloop setting connection arguments

The exit condition was missing.

CC: libav-stable@libav.org

libavformat/librtmp.c

@@ -189,6 +189,8 @@ static int rtmp_open(URLContext *s, const char *uri, int flags)
 
             if (sep)
                 p = sep + 1;
+            else
+                break;
         }
     }
     if (ctx->playpath) {