Previously when listing images via v2, the first image of each batch
was validated against the v2 schema.
This could lead to unpredictable behaviour where a particular image
which failed the schema check may or may not be the first of a batch.
In some cases it also meant that operation by one user could affect the
ability of another other to list images.
Change-Id: I22974a3e3d9cbdd254099780752ae45ff2a557af
Closes-bug: 1477910