Fix file access mode for /run/ddclient/ddclient.conf to fix warnings like:
Sep 09 22:51:40 ddclient[1868]: WARNING: file /run/ddclient/ddclient.conf: file /run/ddclient/ddclient.conf must be accessible only by its owner. Sep 09 22:51:40 ddclient[1868]: WARNING: file /run/ddclient/ddclient.conf: file /run/ddclient/ddclient.conf must not be accessible by others.