[TNU09] Adjust restricted notification

1. Let restricted notification that can be dismissed.
2. Only put up restricted notification when any of tethering is
   activating.

Bug: 154214549
Test: atest TetheringTests
Change-Id: Ib980aca154036828abdab35e3bb11d42f85ff610
Merged-In: Ib980aca154036828abdab35e3bb11d42f85ff610
(cherry picked from commit f4932aff, aosp/1290334)