Revert "pulsesink: uncork if needed upon commit"

Revert "pulsesink: uncork if needed upon commit"

This reverts commit 0dd46accf6d282ff07065852bd91c85c78af3394.

With some audiosinks, starting the ringbuffer on the first commit
causes audio glitches at startup by starting to output segments
from the ringbuffer before it has been filled / fully prerolled. This
doesn't usually happen with pulsesink because we map the pulseaudio
ringbuffer directly, but we should keep things consistent with
other sinks with regards to startup latency, plus it gives more
headway to avoid glitching, should the initial 2nd segment take
more than 10ms to generate.

https://bugzilla.gnome.org/show_bug.cgi?id=657076