Using UserManagerInternal for access control instead of UserManager

Bug: 36067387
Test: for C in {1..10}; do adb shell am instrument -e class com.android.server.pm.ShortcutManagerTest$C \
      -w com.android.frameworks.servicestests/android.support.test.runner.AndroidJUnitRunner; done
      atest CtsDevicePolicyManagerTestCases:LauncherAppsSingleUserTest \
            CtsDevicePolicyManagerTestCases:LauncherAppsProfileTest \
            CtsDevicePolicyManagerTestCases:LauncherAppsMultiUserTest
      atest CtsShortcutManagerTestCases
Change-Id: Ia4ddea58f66861ef760865b6d8831563584f85c9