Cleanup: Remove unnecessary dash escape when building docker container name

We don't need this dash escape since they are not valid name for Container and Pod. Modified test to reflect the changes, and also removed two test cases since they are not allowed in the system anyway. 
If you check for prefix + "--" or prefix + "_", then we will kill stale containers and restart them - non-breaking change.  We can remove the -- check in a couple weeks (leave a TODO)