OMS: Setup state for users on boot and when added

Some users never get switched to (managed profile/work profile) so the
overlay state for a user would never be setup (but they could still show
UI and apps).

This change ensures that user state is setup after an OTA to android O,
and whenever a user is added.

Bug: 37899201
Test: manual (add user via Device Admin sample: vendor/google/tools/DeviceAdminSample)
Change-Id: If214e26e39b18c2861794baf5c608a47d536e5ff

core/java/android/os/UserManager.java

@@ -19,6 +19,7 @@ package android.os;
 import android.Manifest;
 import android.accounts.AccountManager;
 import android.annotation.IntDef;
+import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.annotation.RequiresPermission;
 import android.annotation.SystemApi;
@@ -2129,7 +2130,7 @@ public class UserManager {
      * @return the list of users that were created.
      * @hide
      */
-    public List<UserInfo> getUsers(boolean excludeDying) {
+    public @NonNull List<UserInfo> getUsers(boolean excludeDying) {
         try {
             return mService.getUsers(excludeDying);
         } catch (RemoteException re) {