Override base isAnimating in WindowState

WindowState overrides the isAnimating call. A new base method was added
to handle specific animation types, but the WindowState class was still
overriding the old isAnimating call. Therefore, the check for insets
provider was not handled.

Test: NexusLauncherTests
Fixes: 152657145
Change-Id: I32f5469fa992adb712779a6cb961bd3a1b44a227