Once chutney can verify using relays on IPv6 (legacy/trac#17011/legacy/trac#17153), we should update the unit tests to use descriptors that contain IPv6 addresses in "or-address" lines. This will allow us to unit test legacy/trac#17840 and various other tickets. From legacy/trac#17840: * nodelist_set_consensus: setting ipv6_preferred correctly based on ClientUseIPv6, ClientPreferIPv6ORPort, and ClientUseIPv4.