ethernet: enable testCallbacks_forServerModeInterfaces on CF

testCallbacks_forServerModeInterfaces was previously skipped on CF as
isAdbOverNetwork() was true. The existing interface on CF has configured
NetworkCapabilities which excludes it from being used in tethering.
Using assumeNoInterfaceForTetheringAvailable() is therefore a better
assumption check for this test.

Test: atest EthernetManagerTest
Change-Id: If6cefa519b32d041c8dccc0a58acb3028eefd878
1 file changed