Allow using a log tag in TestableNetworkCallback

For tests that register multiple callbacks, like ConnectivityService
tests, this can make it easier to figure out which callback is getting
called in logs.

Test: atest CtsNetTestCases (tests using this callback)
Bug: 327038794
Bug: 279392981
Change-Id: Ifea5a8180f9667feaadf94c8b927469bafe29590
1 file changed