PresentationSyncTest: disable faster-than-refresh case

As described in the comment, the throughput test that tries to run
faster than the refresh rate makes a couple invalid assumptions. This
change disables that case.

The primary uses of this feature involve producing frames at the
refresh rate or slower.

Bug: 18913338
Change-Id: I27bb72b84732e17341ed270e01f8ba8f02d56b71
1 file changed