Reapply Avoid sending powerhint right after GPU composition.

The change in 8ec87f8c was
unintentionally dropped in moving the code to CompositionEngine.

Bug: 147398431
Test: atest libcomposition_test
Test: go/wm-smoke
Test CtsColorModeTestCases CtsDisplayTestCases CtsGraphicsTestCases CtsMediaTestCases CtsUiRenderingTestCases CtsViewTestCases
Change-Id: Ia652c04abf6e5094b399483948553f2aaffd0aea