Stop search tests using location_settings

Stop robolectric search tests using location_settings, use
sound_settings instead.

The choice of location_settings.xml seems arbitrary, and there's a
commit coming which means one of the controllers doesn't just use
settings to check availability. When the unconfigured mock returns null
from a method, that causes the test to fail in a non-obvious way.

Bug: 171371424
Test: m RunSettingsRoboTests
Change-Id: I4d3386e3c62fb4151e4a4e27625edccec89316d9