readme: make the selinux related command sequence a little clear
readme: make the selinux related command sequence a little clear

bboehmke/docker-gitlab-ci,youhong316/docker-gitlab-ci,youhong316/docker-gitlab-ci,bboehmke/docker-gitlab-ci,adiferd/docker-gitlab-ci,sameersbn/docker-gitlab-ci,outcoldman/docker-gitlab-ci,sameersbn/docker-gitlab-ci,outcoldman/docker-gitlab-ci,adiferd/docker-gitlab-ci