SurfaceFlinger: get present time from SF and not from Scheduler

SF hold the most accurate expected present time as it also knows
whether we are operating at negative offset and which vsync
we are targeting.

Bug: 133241520
Bug: 134589085
Test: systrace when scrolling
Change-Id: I934df3a8bf807b0e52555765a6861f252b69c0d1
Merged-In: I934df3a8bf807b0e52555765a6861f252b69c0d1