Automatic merge from submit-queue

Fix share name generation in azure file provisioner.

**What this PR does / why we need it**:
Azure file share name has a length limit of 63, but currently the code is using data volume's limit 75.

**Which issue this PR fixes**
With current implementation, when the cluster name is long, the resulting file share name could have a length of 75.

Also function `GenerateVolumeName` would produce double '-' when clusterName containing '-' is to be truncated.

In both cases, service would reject the creating file share request.

**Special notes for your reviewer**:
Please refer to:
https://docs.microsoft.com/en-us/rest/api/storageservices/naming-and-referencing-shares--directories--files--and-metadata#share-names

- Share names must be from 3 through 63 characters long.
- The name cannot contain two consecutive hyphens.

@rootfs @colemickens 

**Release note**: