Fixed the catch of the hostname option during ipa-server-install

Originally ipa-server-install would still prompt for the hostname even if it's supplied in the initial installation command.

Ticket: https://fedorahosted.org/freeipa/ticket/2692

install/tools/ipa-server-install

@@ -760,7 +760,7 @@ def main():
         host_default = get_fqdn()
 
     try:
-        if options.unattended:
+        if options.unattended or options.host_name:
             verify_fqdn(host_default,options.no_host_dns)
             host_name = host_default
         else: