Fix CommunalPreferenceControllerTest

Migrate test to robolectric, as this test doesn't require a device to
run. This also speeds up the test, and allows for use of roboelectric
shadows.

Fixes: 337417918
Test: atest CommunalPreferenceControllerTest
Flag: EXEMPT fix broken test
Change-Id: I32b2760c98bf527b33a8ccbe46314395a03da1e0