Jan Alexander Steffens authored Jul 31, 2020 and GStreamer Marge Bot committed Aug 04, 2020

* Trying to disconnect a stream from a running splitmuxsink by flushing
  it results in the FLUSH_START blocking in the stream queue's
  gst_pad_pause_task because the flush did not unblock
  complete_or_wait_on_out, so add a check for ctx->flushing there.

* Add a GST_SPLITMUX_BROADCAST_INPUT so check_completed_gop notices
  flushing changed and the incoming push is unblocked.

* Pass the FLUSH_STOP along to the muxer without waiting.

Part-of: <gstreamer/gst-plugins-good!687>