Clear dream overlay exit animation state when canceling animations.

This changelist ensures that animation state is cleared when animations
are canceled for the dream overlay. There can be other state changes
dependent on the exit animation state being set properly.

Test: atest DreamOverlayAnimationsControllerTest
Fixes: 344620827
Flag: EXEMPT bugfix
Change-Id: Iedcb3049512450cee89b39bf20220966cb965abf