conf: error out on missing dhcp host attributes

In virNetworkDHCPHostDefParseXML an error is reported
when partialOkay == true, and none of ip, mac, name
were supplied.

Add the missing goto and error out in this case.

src/conf/network_conf.c

@@ -746,6 +746,7 @@ virNetworkDHCPHostDefParseXML(const char *networkName,
                              "must be specified for static host definition "
                              "in network '%s' "),
                            networkName);
+            goto cleanup;
         }
     } else {
         /* normal usage - you need at least name (IPv6) or one of MAC