fix Instance table's Flavor Detail popover not showing up

Using the Flavor ID as the unique ID for the popover causes
problems - if you have multiple instance with the same flavor,
the popover would not show up except for the first in the list.

Solution is to have a unique ID using the instance ID.

Change-Id: If3a43b90f524aa780aac4ecece5dbbbbba75137b
Closes-Bug: #1342907
Merge "fix Instance table's Flavor Detail popover not showing up"