bump docker to 18.03.1.ce
bump docker to 18.03.1.ce

Updating to tracking the current release -- no major bugfixes:

https://docs.docker.com/release-notes/docker-ce/#stable-releases

jhoblitt/sandbox-jenkins-demo,lsst-sqre/sandbox-jenkins-demo,jhoblitt/sandbox-jenkins-demo,lsst-sqre/sandbox-jenkins-demo