Automatic merge from submit-queue (batch tested with PRs 49524, 46760, 50206, 50166, 49603)

[OpenStack] Add more detail error message

I get same simple error messages "Unable to initialize cinder client
for region: RegionOne" from controller-manager, but I can not find the
reason. We should add more detail message "err" into glog.Errorf.

Currently NewBlockStorageV2() return err when failed to get cinder endpoint, but there is no code to output the message of err.

**Release note**:
```release-note
NONE
```