Automatic merge from submit-queue (batch tested with PRs 44625, 43594, 44756, 44730)
Check for terminating Pod prior to launching successor in StatefulSet
Modifies sync loop for StatefulSet controller to check if a Pod is terminating before launching its successor. Fixes#44229. Should be cherry picked into 1.6 branch.
**Which issue this PR fixes**
fixes#44229
```release-note
NONE
```