Automatic merge from submit-queue
image name must not have leading or trailing whitespace
**What this PR does / why we need it**:
verifies that an image name can not have leading or trailing whitespace
**Which issue this PR fixes**
fixes https://github.com/kubernetes/kubernetes/issues/47490
**Special notes for your reviewer**:
i was surprised we had not caught this, so if there is an image spec that says leading and trailing whitespace is a good thing, i am open to correction.
i was made aware of downstream users of validate pod template spec that used " " as a special token. as a result, i only do the validation of image name " " in the `Pod` only.
**Release note**:
```release-note
NONE
```
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