Correct some issues with L3 extension

Change-Id: Id3e941e3416c80e8150c341e69c2ef29282139a0
author: diane fleming
Add missing snapshot metadata calls

Include note about case-sensitivity of key names

Closes-Bug: #1257936

Change-Id: If057cc65860cbcca3f2ad66868470f6a9bd9dc71
author: diane fleming
Merge "Add missing snapshot metadata calls"
Merge "Correct some issues with L3 extension"
Add virtual_size attribute to list images response

Closes-Bug: #1279866

Change-Id: Id2c5e05b3040d0829a4f8b1834f6410f043d7fff
author: Diane Fleming