Fix issue where keyguard reports a valid token but doesn't draw

This fixes an issue where keyguard isn't showing but tells
PhoneWindowManager to wait anyway.  The fix is to send a null token
when keyguard isn't showing.

Fixes bug 11216030

Conflicts:
	packages/Keyguard/src/com/android/keyguard/KeyguardViewManager.java

Change-Id: I99a963e098a2c725b4fa797390e3ff480954b5bf