fixes #18540 - update domain on primary in hosts_count tests
domain/domain_id are not attributes of the host itself, they're delegated to the primary interface. When using update_attribute on the host, the model doesn't appear `changed?` so Rails 5 skips the save.
The test "should update hosts_count" is left with delegation as the direct interface modification is tested in the next test.
Related issues
Bug #18540: Host#update_attribute(domain: ...) tests fail on Rails 5, model not saved
fixes #18540 - update domain on primary in hosts_count tests
domain/domain_id are not attributes of the host itself, they're
delegated to the primary interface. When using update_attribute on the
host, the model doesn't appear `changed?` so Rails 5 skips the save.
The test "should update hosts_count" is left with delegation as the
direct interface modification is tested in the next test.