Also check idle to handle stopping activities

Animating activity may not have nowVisible=true (see
WindowSgtate#updateReportedVisibility) but it may be
already idle.

This restores the same condition as before commit edc42940.

Bug: 185807984
Test: atest DreamManagerServiceTests# \
            testStartTurnScreenOnActivityDoesWake
Change-Id: Iaaffb80bd9e1e339d36034bdb6a369562f59a41c