adapt Dockerfile for running on openshift

[carlobongiovanni]

Hi,

I'm trying to work on this issue open-horizon/devops#80, but to fix it we would need to update all Dockerfiles from OH to make them able to run in the new environment.

By default Openshift runs containers assigning them an arbitrarily assigned user ID, therefore requiring to make changes to support such a type of configuration.

I have prepared a fix and tested it on a local deployed Openshift cluster, I will use this issue (if you accept it) as a reference to push my changes once they are finalized.

Best
C.