keepalived: add script security param to fix warning

Openwrt is a single user system. So keepalived is runnig as root.
If we add the config options `script_user root` and
`enabled_script_security' the following warnings are gone.

> local1.info Keepalived_vrrp[5382]: SECURITY VIOLATION - scripts are
being executed but script_security not enabled.

Signed-off-by: Florian Eckert <fe@dev.tdt.de>

net/keepalived/files/keepalived.init

@@ -98,6 +98,9 @@ print_notify() {
 globals() {
 	local notification_email
 
+	printf '%bscript_user root\n' "${INDENT_1}" >> "$KEEPALIVED_CONF"
+	printf '%benabled_script_security\n' "${INDENT_1}" >> "$KEEPALIVED_CONF"
+
 	config_get notification_email "$1" notification_email
 	print_list_indent notification_email