PhoneWindowManager: Make sure KeyDisabler is always called on boot

* Otherwise, some KeyDisabler classes are left in a weird state
* Because we don't keep track of whether an initial state was ever set,
  we never call KeyDisabler on boot if the setting is set to 0
* To remedy this, keep track of whether an initial state was set

Change-Id: Ib432ed3278dd8f4f4cba3ba488879b3c1cd9c8f4