Refactor PodStatus to PodCondition in internal API for v1beta3

Change PodStatus (string) to PodCondition (string) to make space for new PodStatus (struct) in v1beta3 API.

Change the constant values for Pod statuses to match v1beta3 API.
I switched it to Failed, as you suggested in those two cases you hightlighted.

There is a larger issue, I think, with containers expressing their state better (succeeded, failed, or otherwise) and having their state stored in etcd.  AFAICT, status is calculated at runtime when requested by the API.  Some on the Open Shift team have expressed interest in knowing the runtime state of pods, querying for them by status, etc. I don't think they can do that easily today.     but that is another issue.