LocationManagerService now listens for changes to settings,
making LocationManager.updateProviders() unnecessary.
Removed LocationManager.updateProviders()
Added Settings.Secure.setLocationProviderEnabled(), which is a thread-safe way
of enabling or disabling a single location provider.
This is safer than reading, modifying and writing the LOCATION_PROVIDERS_ALLOWED directly.
BUG=1729031
Automated import of CL 144372
