Display instances with no image information

When booted from volume, instances do not have an image reference/id.

Change-Id: I107c096a50c6a49e2a25c3b29b7d5c3273e4348e
Closes-Bug: #1239896
Merge "Display instances with no image information"
Revert patch causing Instance Image Perf Issue

The previous patch https://review.openstack.org/52115 is causing
image get call for each instance. Reverting this back.

Fix will follow in another patch.

Related to bug: Bug: #1239896

Change-Id: If0d6feba50eb3f45248019fcc48580d1eae60d67
Improve display of instance image information

When instance is booted from volume image it returns a string,
while for instance from image returns a dict. Fix is made to
handle both cases.

Change-Id: I23aeccd21f88a353222d3fc7dc4b5c337c2bfecb
Closes-Bug: #1239896