stopTethering with a TetheringRequest should only stop tethering if
there is an existing request (pending or serving) that fuzzy-matches the
input and whose UID matches the caller (unless the caller is Settings,
which is allowed to remove any request).
If there is no existing fuzzy-matched request, return
TETHER_ERROR_UNKNOWN_REQUEST.
Note: This was originally merged as aosp/3527440 but was reverted due to
a dependency CL being reverted. Remerging this on top of the fix for the
dependency CL.
Reverted changes: /q/submissionid:3541662-revert-3527440-JRJJTQBUFC
Bug: 216524590
Test: atest TetheringTest RequestTrackerTest TetheringManagerTest
Change-Id: I99dd2433efbb82f3721aa708ab50d198f6fbcb10
d093ea69b0