Skip testDefaultNetworkActiveListener on R devices.

testDefaultNetworkActiveListener was flaky on R.
NetworkActivityTracker is not mainlined before S and behavior on R has
difference.
This CL skips the test on R since NetworkActivityTracker behavior on R
is not updatable and updating the test to solve the test flake on R does
not have much benefit.

Bug: 285768880
Test: atest ConnectivityManagerTest
Change-Id: I68c444d587d94b18ed5a58c6d3a05db7b51e2775
1 file changed