Remoting testsuite has hard-coded IPv6 addresses making it less portable and this is not cool because we are using the testsuite for platform certification. Not all machines have properly configured (or support) IPv6 stack. In either way, the TS should be able to test both stacks.
I suggest to use common alias "localhost" and only control via -DpreferXY to select IPv4 or 6 stack. AFAIR the systems have alias localhost for both addresses. Let me know if there is an issue with this approach (will attach commit/ pull request).