Fix WhenToDreamPreferenceControllerTest

The current test uses a mock context, which doesn't support all the
methods being used. Instead, switch to using a real context.

Test: make -j64 RunSettingsRoboTests ROBOTEST_FILTER="com.android.settings.dream.WhenToDreamPreferenceControllerTest"
Bug: 216036457
Change-Id: Ib431d27943a8a732da1ef2dfad2eb1ce7ede36c2
1 file changed