Add tests for HibernatedAppsPreferenceControllerTest

Add tests for getNumHibernated in HibernatedAppsPreferenceController
based off the major use cases.

Bug: 187745929
Test: atest HibernatedAppsPreferenceControllerTest
Change-Id: I7bee75075f12fc1661f1b12da82e6ccb16eaa06d
1 file changed