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
```