To be the unbundled application, tethering can not use UserManagerInternal
method anymore. Replace it by listening user restriction change intent.
Also fix some cleanup from
https://android-review.googlesource.com/c/platform/frameworks/base/+/1131002
Bug: 143195885
Test: -build, flash, boot
-atest TetheringTests
-manual test. Add a trigger point to call
UserManager.setUserRestriction(DISALLOW_CONFIG_TETHERING) from
Settings. Open hotspot -> restrict tethering from new adding trigger
point -> hotspot is OFF and Tethering settings are not available.
Change-Id: I4ed08d20f8b7476b8ecd5d018b75806dd2f22cc1
Merged-In: I4ed08d20f8b7476b8ecd5d018b75806dd2f22cc1