Fixes notification blocking from secure camera.

This change modifies the code in StatusBar which determines whether to
show the bouncer when the user attempts to change notification settings
such that it correctly checks the state of the keyguard.  This fixes an
issue where the bouncer was not shown when changing notification
settings from the secure camera.

Change-Id: Ieb59c49c4b790e38a9dcf79e8777f89318d11946
Fixes: 117888590
Test: manually