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