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Fix kubectl explain for cronjobs

**What this PR does / why we need it**:
`kubectl explain cronjob` was failing with `error: Couldn't find resource for "batch/v1, Kind=CronJob"` the reason for that is that even though we were getting the group and version from the mapper, we always rewrote it with the default value for a specific group, unless user specified the output version. 


**Special notes for your reviewer**:

**Release note**:
```release-note
Fix kubectl explain for resources not existing in default version of API group
```
for review:
/assign @juanvallejo 
for approval:
/assign @deads2k