LocationSettingsActivity: Account for deprecated location modes

LOCATION_MODE_HIGH_ACCURACY, LOCATION_MODE_SENSORS_ONLY and
LOCATION_MODE_BATTERY_SAVING are deprecated.

Take one further step and refactor the entire logic to call
LocationManager#setLocationEnabledForUser(boolean, int) instead
of setting location mode and LocationManager#isLocationEnabled()
to check if location is enabled.

Change-Id: Ibe1930902f6bfff99eb2c2d852ab600620e25f08