Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Allow env to be updated via specific key in resource

**What this PR does / why we need it**:

This change allows users of the `oc` client to specify a list of comma-separated keys when running `oc set env` which should be imported from a resource i.e configmap or secret

This can be useful when a number of applications want to share a configuration object but don't want to pollute a resource with unused environment 



**Release note**:

```release-note
Allow kubectl env to specify which keys to import from a config map
```