Prevent infinite layout and wallpaper flashing

Prevent infinite layout and wallpaper flashing

The original logic would cause mTopFullscreenOpaqueWindowState to be
hidden in PhoneWindowManager.finishPostLayoutPolicyLw(), and to be
shown in WindowAnimator.updateWindowsLocked() continuously if there
is a show-when-locked dialog.

The wallpaper would be hidden after the original wallpaper target is
hidden, before the new wallpaper target is shown.

https://code.google.com/p/android/issues/detail?id=162495

Change-Id: I918e0fa03eec38d9f0c07150c17013c6c21683cb