Comment 2 for bug 1252185

It is because nova-list and nova-show api does not provide volume information.

"nova show ca3a7f40-8cdb-4928-92c1-e099e90b6c45" cmd actually returns a hard code string "Attempt to boot from volume - no image supplied" if image field is empty. The string is "-" in Horizon when the image field is empty.

I do not think the instance list should contain the volume info, because
1. it requires extra api calls to cinder, which has impact to performance when loading instances list
2. user can see the volume info in "Instance Details" page