Clear all pending transactions on screen wakeup

If an app sets a transaction that modifies layer state, but does not get
committed by an SF composition cycle, we may end up dangling some
callbacks.  Temporary fix is to clear and send callbacks on wakeup

Bug: 141111965
Test: build, boot, manual
Change-Id: I781124c3f96174cefd5eb67e597c13f923df4fc1