SF: fix expected vsync time when changing work duration

When changing the work duration for a scheduled callback, we should
apply it on the next frame only if we would skip a callback call.
This change fixes the condition where we apply a different work
duration that doesn't change the wake up time but rather changes
the expected vsync time.

Test: TouchLatency bouncy ball + expand notification shade
Bug: 191969790
Change-Id: I067693fe361200a6f899bd81b74d8a1a155a452d