Don't remove a user already being removed.

Check if UserManager is already removing
a user before starting to remove it.

Bug: 15583858
Change-Id: If9763e9b47355d9ae35cc621367c74725029aa90

services/core/java/com/android/server/pm/UserManagerService.java

@@ -1104,7 +1104,7 @@ public class UserManagerService extends IUserManager.Stub {
             final UserInfo user;
             synchronized (mPackagesLock) {
                 user = mUsers.get(userHandle);
-                if (userHandle == 0 || user == null) {
+                if (userHandle == 0 || user == null || mRemovingUserIds.get(userHandle)) {
                     return false;
                 }
                 mRemovingUserIds.put(userHandle, true);