Clear the previous unlock request. Subclasses should clear
any state they set during #GstBaseSinkClass::unlock, and be ready to
continue where they left off after gstbase.base_sink.BaseSink.waitPreroll,
gstbase.base_sink.BaseSink.wait or gst_wait_sink_wait_clock() return or
#GstBaseSinkClass::render is called again.
Clear the previous unlock request. Subclasses should clear any state they set during #GstBaseSinkClass::unlock, and be ready to continue where they left off after gstbase.base_sink.BaseSink.waitPreroll, gstbase.base_sink.BaseSink.wait or gst_wait_sink_wait_clock() return or #GstBaseSinkClass::render is called again.