Backup unable to mount archive on AKS with AzureFile

As initially observed in K8S-2134 backup is failing when attempting to use azure file as the storage class. 

I've gone though source code for backup and this appears to be the portion of code resulting in error:

// There is no archive version file. If the directory is empty then we can create an archive directory if we are allowed to.

if !options.Create {

  return nil, OpenError{path, errors.New("Not an archive directory")}

} 

Which means the Create flag on the Mount Options is somehow being set false.  This might be due to securityContext used when the volume is mounted as we've also noticed that the Couchbase user id is 8543 rather than 1000 for the backup container.