qtmux: avoid fallthrough to moovrecovery failure section

Return before that to preserve our successfull results, otherwise no
moov recovery information would be written

https://bugzilla.gnome.org/show_bug.cgi?id=771478

gst/isomp4/gstqtmux.c

@@ -2094,6 +2094,8 @@ gst_qt_mux_prepare_moov_recovery (GstQTMux * qtmux)
     }
   }
 
+  return;
+
 fail:
   /* cleanup */
   fclose (qtmux->moov_recov_file);