Fix testcase error

- ignore testcase in MobileNetworkActivityTest
- To avoid null pointer access in LocationForWorkPreferenceController,
move mUserManager initialization in constructor

Test: make RunSettingsRoboTests ROBOTEST_FILTER="com.android.settings.search"
Change-Id: Icf6c36ecef22149def6d5924741a798e8f506033
2 files changed