Make "kerberos" test suite independent of "localhost" name resolution.
This suite malfunctioned if the canonical name of "localhost" was
something other than "localhost", such as "localhost.localdomain". Use
hostaddr=127.0.0.1 and a fictitious host=, so the resolver's answers for
"localhost" don't affect the outcome. Back-patch to v11, which
introduced this test suite.
Discussion: https://postgr.es/m/
20180801050903.GA1392916@rfd.leadboat.com