aggregator: need gst_aggregator_pad_set_nowait() for sparse streams
Submitted by Tim Müller
We need a way to tell GstAggregator to never wait for data on certain pads.
This is needed for sparse inputs where we may not always get data or regular GAP events.
Without this, a muxer in non-live mode will just lock up if it doesn't receive data or GAP events on one of the input pads, and in live mode we will always end up with the maximum configured latency since we'll always wait and time out.