SurfaceFlinger: clamp frame refresh duration to min refresh duration

Some applications may send doubles frames which are scheduled to be
presented very close to each other. In this case to avoid calculating
a very high fps for the layer, clamp the refresh duration to the minimal
value allowed for the layer.

Test: YouTube play "YouTube 60fps Tester" video.
Bug: 139209733
Change-Id: I4bcdfad65b57782ec6e346e8d884bfb6e2abac4d