[SP21.1] Address comments for API council review about aosp/1172143

This is modified since the shape of API is changed in the
counter-part CL.

Test: atest TetheringTests FrameworksNetTests FrameworksTelephonyTests
Fix: 148552904
Change-Id: I64cf5b9c1a775200bc89d93b404d546f41d259d1
Merged-In: I64cf5b9c1a775200bc89d93b404d546f41d259d1
(cherry picked from aosp/1253424)