Automatic merge from submit-queue
hide operator when describe pod with empty value tolerations
**What this PR does / why we need it**:
The tolerations printing in `kubectl descirbe pod` is not correct when toleration.value is empty, this PR is to fix it.
Before:
```
Tolerations: node.alpha.kubernetes.io/notReady=:Exists:NoExecute for 300s
node.alpha.kubernetes.io/unreachable=:Exists:NoExecute for 300s
```
After:
```
Tolerations: node.alpha.kubernetes.io/notReady:NoExecute for 300s
node.alpha.kubernetes.io/unreachable:NoExecute for 300s
```
Also updated tests to cover all possible cases of describing pod with tolerations. See changes in of `TestDescribePodTolerations()` in `describe_test.go`
**Which issue this PR fixes**:
**Special notes for your reviewer**:
**Release note**:
```release-note
NONE
```