base: don't show global actions if shutdown sequence was started

Change-Id: Icd77aa7529faf438dcc80e45434826465a11aab8
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>

Conflicts:
	core/java/android/view/WindowManagerPolicy.java
	policy/src/com/android/internal/policy/impl/PhoneWindowManager.java