fixes #6358 - Update LookupValue fqdn matchers when a host is renamed

Looks good to merge.  @domcleal, @ohadlevy, @GregSutcliffe, can I get another ACK before merging.

@treydock, nitpick, the expectation for assert_equal is the first argument. If there's a failure, minitest will output "expected 'first arg', but 'second arg'". It's fine to merge as is. Just a FYI.