pipeline: Allow up to 2 seconds queueing in the playsink video queue
In playsink the default video queue max size is 3 buffers, which is sometimes not enough for our use case. Allow up to 2 seconds of buffered data, giving us more time to do the transition between clips, and thus avoiding dropping frames in the sink when bringing up new clip takes too much time. Differential Revision: https://phabricator.freedesktop.org/D1854