Driver merge review comments from 111425

This review contain fixes that addresses the review comments raised in
https://review.openstack.org/#/c/111425 revision 19 and 22.
Once these changes are merged here in Ironic, they will be
proposed as updates to the patch series over in Nova.

Change-Id: Idf4ea36670e5832600c5ff5f814e06aa096e156e
Merge "Driver merge review comments from 111425"