rtmpproto: Fix limelight authentication with abbreviated app names

When streaming to limelight, the app name is either a full
"appname/subaccount" or "appname/_definst_". In the latter case,
the app name can be simplified into simply "appname", but the
authentication hashing assumes the /_definst_ still to be present.
Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/rtmpproto.c

@@ -1612,6 +1612,8 @@ static int do_llnw_auth(RTMPContext *rt, const char *user, const char *nonce)
     av_md5_update(md5, method, strlen(method));
     av_md5_update(md5, ":/", 2);
     av_md5_update(md5, rt->app, strlen(rt->app));
+    if (!strchr(rt->app, '/'))
+        av_md5_update(md5, "/_definst_", strlen("/_definst_"));
     av_md5_final(md5, hash);
     ff_data_to_hex(hashstr2, hash, 16, 1);
     hashstr2[32] = '\0';