Throttling CTS producing frame speed

Throttling CTS producing frame speed

CTS checks the present time of the frame 6 frames ago. However, if
the default buffer count of BufferQueue is more than 7, CTS could
produce frames continuously in a short time. In this case, the frame
6 frames ago might be not presented yet then CTS fails. To prevent
this situation, CTS produces frames at the speed according to
compositeInterval.

Component: EGL

Affected tests:
dEQP-EGL.functional.get_frame_timestamps.*

Change-Id: I1ac15974a6c4147ee2546ad21dea1fb3e6bf38f9