Automatic merge from submit-queue (batch tested with PRs 49276, 49235)
Don't fail fast if LoadBalancer section is missing
**What this PR does / why we need it**:
We should allow scenarios where cinder can be used even if the
operator does not want to use the openstack load balancer. So
let's warn in the beginning if subnet-id is missing but fail only
if they try to use the load balancer
**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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