Investigate use of jclouds for on-demand infrastructure

See if we can leverage https://jclouds.apache.org/ to dynamically allocate Jenkins nodes for use by longer running jobs, and container testing.

Related:
1) https://wiki.jenkins.io/display/JENKINS/JClouds+Plugin
2) @karianna mentioned the security team has recommendations related to this type of infra model, which will be shared at some point.

Start with the jclouds website and the linked JClouds Plugin wiki page, then examine how the infrastructure repository provisions Jenkins nodes. Determine whether dynamic allocation supports longer-running jobs and container testing, and document the feasibility plus the security team's recommendations when they are available.

Written by the indexing model from the issue text.