Fix problem where PhoneWindowManager waits for keyguard to draw

This fixes a problem where PhoneWindowManager times out waiting
for keyguard to draw when it's disabled.  Instead, we pass a null
token back which allows PhoneWindowManager to continue.

Fixes bug 11190932

Change-Id: I041ea1d88dca681476d9477a3aab54559976b312
Merge "Fix problem where PhoneWindowManager waits for keyguard to draw" into pac-4.4