Don't try to launch broadcast receivers during boot

It turns out that sysUI visibility / interactivity is racing with
boot, and it's possible in some circumstances for the user to start
the secure camera swipe gesture before formal boot-completed.  Make
sure we only send the camera-related broadcast to registered
receivers in that case, otherwise we'll implicitly be asking to
launch other apps before boot, which is forbidden.

Bug 19060618

Change-Id: I7fcf13b5af7b2edfbb4aac06ef04a0fde2c6a0f7