Disable dreams home controls button when disabled on lockscreen.

When home controls are disable on lockscreen, we should also disable
them on dreams.

Bug: 282680621
Test: flashed device, disabled/enabled home controls on lockscreen and
verified that dreams home controls button was hidden/shown correctly
Test: make -j64 RunSettingsRoboTests ROBOTEST_FILTER="com.android.settings.dream.DreamHomeControlsPreferenceControllerTest"

Change-Id: I535b079cabc2838e77f3afc74bb8f8730b850653