IS-04-03: Nodes may fail test_01 if another Registry's advertisements are discoverable

[garethsb]

If another Registration API is advertised by mDNS (or with unicast DNS-SD records) on the same network as the Node under test, the Node may fail IS-04-03 test_01 even, in the case of unicast DNS-SD advertisements, if the advertised Registry does not respond, because the Node may not enter peer-to-peer operation.

This could be suggested in the failure message, even if it's not possible for the test suite to detect such advertisements itself.

[garethsb]

@rhastie, I think this is the final issue we saw.

[andrewbonney]

Relates to https://github.com/AMWA-TV/nmos-testing/issues/344