Add values for empty sahara dropdown boxes

Currently if no templates or images are available then the drop down
boxes simply appear empty, this patch adds "No Images Available" and
"No Templates Available" as the first item in each list if they are
empty.

Change-Id: I4bfed9b53f5ac9f031c23a15270b996f7d153be5
Closes-Bug: 1391343
Merge "Add values for empty sahara dropdown boxes"