Improve some javadoc related to isProviderEnabled() apis

- LocationManager.isProviderEnabled() no longer throws SecurityException:
the caller could already circumvent the permission check by calling
Secure.isLocationProviderEnabled()

Change-Id: I5abd04264299671ed35ce4594b5be46d86378767
diff --git a/services/java/com/android/server/LocationManagerService.java b/services/java/com/android/server/LocationManagerService.java
index de29155..f70f4db 100644
--- a/services/java/com/android/server/LocationManagerService.java
+++ b/services/java/com/android/server/LocationManagerService.java
@@ -1773,8 +1773,12 @@
 
     @Override
     public boolean isProviderEnabled(String provider) {
+        // TODO: remove this check in next release, see b/10696351
         checkResolutionLevelIsSufficientForProviderUse(getCallerAllowedResolutionLevel(),
                 provider);
+
+        // Fused provider is accessed indirectly via criteria rather than the provider-based APIs,
+        // so we discourage its use
         if (LocationManager.FUSED_PROVIDER.equals(provider)) return false;
 
         int uid = Binder.getCallingUid();