Fix NetApp cDOT driver use of Glance locations

Fix NetApp cDOT driver use of Glance locations

As of Kilo, Glance returns a list of locations associated with an
image, but the NetApp cDOT driver only operated on the first one.
In addition, Glance has started enforcing a schema on the metadata
that can be added to images stored in the file glance_store. This
change modifies the cDOT driver to iterate through the list of
locations, using the correct schema-compliant fields, and uses the
first one with a valid IP address for our backend for optimizing
the copy of images into Cinder volumes.

Co-authored-by: Tom Barron <tbarron@dyncloud.net>
Closes-Bug: #1461116

Change-Id: Ia788aea5110b74833c6a0594f26c9727e06fd87e