resolver modification should notify docker service

Containers running use /etc/resolv.conf of the host. By, the modern resolver use 127.0.1.1 and can not be used inside container. So we use old format in resolver : https://gitlab.adullact.net/adullact/puppet-gitlabrunner/blob/master/manifests/init.pp#L80

But we have to ensure that docker engine is started after the resolver modification.