Guard window and transition animation scales with a lock

mWindowAnimationScaleSetting and mTransitionAnimationScaleSetting
weren't guarded by locks (and they were not volatile either) in
WindowManagerService even though they get updated via binder threads.
This change guards them with mGlobalLock.

Test: atest WindowManagerServiceTests
Fixes: 432406193
Flag: EXEMPT bugfix
Change-Id: I7183426196c5b93a4441a987f025f3905ab4cb13