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**:

```
NONE
```