Only apply early offsets when transaction has been applied

This avoids a race where we decrement the early offset count in
postComposition() before the transaction applying early offsets has
actually been applied, so we're in early offsets for too few frames.

Bug: 158127834
Test: photos launch
Test: systrace

Change-Id: If7a7d12fa466ee4d163210263b7f02f7a74b3280