SF: Don't update scheduler if desired active mode is not allowed

Currently if we the desired active mode is not allowed
we call desiredActiveModeChangeDone which also updates
Scheduler with the desired mode. We should instead clear the
desired mode.

Bug: 190982486
Test: atest libsurfaceflinger_unittest
Change-Id: I349fe3f14f4075be9e816b2d319e78603b27727d