Automatic merge from submit-queue
remove unused function in openstack cloud provider
**What this PR does / why we need it**:
List function not used in openstack cloud provider, and useless, I think need remove it.
**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**:
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NONE
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9aa04c755f