Update the theme to fix background color problem

The action bar in the some setting pages has different background colors
when the action bar is in collapsed mode. These pages are using the default
settings theme that doesn't include edge-to-edge setting. This can be
fixed by assigning SubSettings theme to this activity.

Fix: 189189879
Fix: 188110157
Test: visual verified
Change-Id: Ie8d9b4c950e6a8ab5a7e361f94b8587d854b3b70