Tune scheduling a bit, avoid a binder ipc

Don't query running behind if it's not possible to be behind such
as having received a vsync since the last call to swap buffers.

This also avoids an accidental-starvation issue where if surface
flinger was a bit sluggish to dequeue then renderthread would drop
thinking the queue was full.

Also be a bit smarter about tracking if we've already drawn for this
vsync target to avoid producing two frames for the same vsync

Change-Id: Ib266500a693c27000b2e8ea578f111229d75147a