Use isLocationProviderEnabled to test for enabled providers

LocationManagerService was just checking if the string of (comma-separated)
Location Providers contained the provider we were interested in.  This works
fine in normal cases, but breaks if we add a provider such as test_network.
Enabling test_network causes LocationManagerService to think that the network
provider is also enabled.

The code in Settings.Secure.isLocationProviderEnabled() checks for the commas
in the string as well, to make sure that a provider name which is a substring
of another provider name won't cause problems.  It also centralizes the code
which reads the string.

Signed-off-by: Brad Larson <brad.larson@garmin.com>

services/java/com/android/server/LocationManagerService.java

@@ -552,10 +552,8 @@ public class LocationManagerService extends ILocationManager.Stub implements Run
         }
         // Use system settings
         ContentResolver resolver = mContext.getContentResolver();
-        String allowedProviders = Settings.Secure.getString(resolver,
-           Settings.Secure.LOCATION_PROVIDERS_ALLOWED);
 
-        return ((allowedProviders != null) && (allowedProviders.contains(provider)));
+        return Settings.Secure.isLocationProviderEnabled(resolver, provider);
     }
 
     private void checkPermissionsSafe(String provider) {