add support for skopeo for copying docker images between clusters without requiring docker socket access

[jstrachan]

background: http://rhelblog.redhat.com/2017/05/11/skopeo-copy-to-the-rescue/

related:

• https://trello.com/c/8nTMn9fV

[jstrachan]

wonder if we need to add it as a binary to the clients docker image?

[lpsantil]

@jstrachan Do you mean something like this?

https://github.com/redhat-cop/containers-quickstarts/tree/master/jenkins-slaves/jenkins-slave-image-mgmt

[jstrachan]

@lpsantil yes! I figure we should be able to add skopeo as a standard function to the library; then look at using it by default to move images between environments.

Maybe the simplest solution is to add skopeo to our current clients image then its available OOTB in all pipeline build pods? https://github.com/fabric8io/fabric8-pipeline-library/#understanding-how-it-works