Doing the following:
- Create 2 smart proxies, one for dhcp/dns/tft/puppetca/puppet, another for realms. Let's keep the realms proxy off, so it's unreachable.
- Create a hostgroup A that sets domain, subnet, realm, puppet_proxy, puppet_ca_proxy
- Create a host that uses hostgroup A, but uncheck 'inherit' and remove the 'realm' attribute. The host is created just fine with no realm
- When I try to rebuild the host, `HostBuildStatus#check_all_statuses` is called. This checks the host_status (OK), templates_status(OK), and smart_proxies_status(FAIL). The host cannot be rebuilt.

The reason `smart_proxies_status` fails is that `smart_proxy_ids` tries to find whether Realm is set.
- If it's set, it adds the proxy to 'Host#smart_proxies`
- If it's not set, it looks in the hostgroup to see if it's set there. However, I have overridden the option, because I don't want to set a Realm since I don't want to boot the Realm proxy I have.

Host#smart_proxies should not look in the host.hostgroup object to retrieve values for the proxy, but instead retrieve those from itself