Use the new Jenkins slave agents

[donovanmuller]

There are new Jenkins slave agents being added and we should update to using those as a base when they are available.

[donovanmuller]

Images are pushed to Docker Hub:

• https://hub.docker.com/r/openshift/jenkins-agent-nodejs-8-centos7
• https://hub.docker.com/r/openshift/jenkins-agent-maven-35-centos7

[chriskieser]

The current ones might be deprecated. So more future proofing