Add support for creating multiple ifaces with RA responders

The RA responder is needed in order to properly provision interfaces in
the ethernet tests. This CL wraps the tap interface creation and
destruction inside a small helper class.

Test: atest CtsNetTestCases:EthernetManagerTest
Change-Id: Id92a233873f2f8a738ca563f507a2ead4478aebc
1 file changed