Quoting from the manual about DBHost:
```
In case of MySQL localhost or empty string results in using a socket. In case of
PostgreSQL only empty string results in attempt to use socket.
```
https://www.zabbix.com/documentation/2.0/manual/appendix/config/zabbix_server
With this commit we should avoid some race conditions in systemd, because if the
host is set to "", there is no condition that postgresql has to be started prior
to the Zabbix server.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
62d5282602