Automatic merge from submit-queue (batch tested with PRs 48381, 48274)
Fix completions for --namespace to override kubectl flags
**What this PR does / why we need it**:
This PR fixes completions for --namespace to override kubectl flags. Due to not using __kubectl_parse_get, __kubectl_get_namespaces doesn't support to override kubectl flags.
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #
**Special notes for your reviewer**:
**Release note**:
```release-note
NONE
```
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