Take home controls setting into account

Fixes bug where the home controls quick affordance configuration fails
to actually listen for changes in the settings for showing home controls
on the lock-screen.

Fix: 241693714
Test: Updated unit tests. Manually verified that the quick affordance
for home controls shows up on the lock-screen only when Settings >
Display > Lock screen > Show device controls is enabled.

Change-Id: Id316e61539469c44fe16884852a9b8dd342dcc07