SF: check previous present fence to avoid early presentation

If SurfaceFlinger finishes composition a vsyncPeriod or more before it
planned to, it sleeps before calling composer to present the frame to
avoid early presentation. In this CL we are removing the sleep if the
previous present fence is still pending, as early presentation is not
possible (composer has already a frame queued).

Bug: 190842189
Test: Bouncy ball while forcing client composition
Change-Id: Id913a21b3489973d82498c6154843656972b6e1a