OpenVPN servers using udp6 or tcp6 fail to start, closes...

OpenVPN servers using udp6 or tcp6 fail to start, closes https://github.com/opnsense/core/issues/1576

(cherry picked from commit daa58810)
(cherry picked from commit 3abd54ae)

src/etc/inc/openvpn.inc

@@ -457,9 +457,10 @@ function openvpn_reconfigure($mode, $settings, $device_only = false)
     if (is_ipaddr($ipaddr)) {
         $iface_ip=$ipaddr;
     } elseif (!empty($interface) && $interface != "any") {
-        $iface_ip=get_interface_ip($interface);
-        if (empty($iface_ip)) {
+        if (stristr($settings['protocol'], "6") !== false) {
             $iface_ip = get_interface_ipv6($interface);
+        } else {
+            $iface_ip = get_interface_ip($interface);
         }
     }