dhcp: fixup inconsistent authoritative usage

PR: https://forum.opnsense.org/index.php?topic=2826.0

src/etc/inc/services.inc

@@ -497,10 +497,10 @@ one-lease-per-client true;
 deny duplicates;
 ping-check true;
 update-conflict-detection false;
+authoritative;
 
 EOD;
 
-
     $dhcpdifs = array();
     $add_routers = false;
     $gateways_arr = return_gateways_array();
@@ -1205,17 +1205,10 @@ one-lease-per-client true;
 deny duplicates;
 ping-check true;
 update-conflict-detection false;
+authoritative;
 
 EOD;
 
-    if (!isset($dhcpv6ifconf['disableauthoritative'])) {
-        $dhcpdv6conf .= "authoritative;\n";
-    }
-
-    if (isset($dhcpv6ifconf['alwaysbroadcast'])) {
-        $dhcpdv6conf .= "always-broadcast on\n";
-    }
-
     $dhcpdv6ifs = array();
     $dhcpv6num = 0;
     $nsupdate = false;