aggregator: send flush_stop ourselves if needed
In !159 (merged) , we switched to sending flush_start ourselves from the do_seek implementation. If no flushing seek successfully made its way upstream, we need to send flush_stop ourselves as well.
In !159 (merged) , we switched to sending flush_start ourselves from the do_seek implementation. If no flushing seek successfully made its way upstream, we need to send flush_stop ourselves as well.