Automatic merge from submit-queue
Retry calls to ReadFileViaContainer in PD tests
**What this PR does / why we need it**:
kubectl exec occasionally fails to return a valid output string. It seems to be an issue with docker #34256. This PR retries the 'kubectl exec' call to workaround the issue. This should fix the flaky PD test issues.
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes#28283
**Release note**:
NONE