Flush pending changes when desktop starts

Flush pending changes when desktop starts

The system to avoid processing changes for a stopped desktop was a
bit overly aggressive and resulted in those changes getting stuck even
when the desktop started again (yet another change was needed to get
things rolling again).

Make sure we flush out anything pending once the desktop is back up and
running. We don't use the frame timer here as we no longer know how
old these changes are, so we're not really rate limiting any application.