[Predictive Back] Fix bug where closing task bar's all apps will show scale...

[Predictive Back] Fix bug where closing task bar's all apps will show scale animation even if predicitve back is disabled

TaskbarAllAppsSlideInView.onBackInvoked() can be triggered by ViewGroup.dispatchKeyEvent(event) with KEYCODE_BACK, in that case we should skip scale animation

Test: manual
Fix: b/272317866
Change-Id: I19468cfe4765de5276c479b0f7fa88ec0690bbfd