Ensure disk_ and container_format during upload

This patch changes the image domain model so that the transition from
'queued' to 'saving' or 'active' status cannot take place if the image's
disk_format or container_format are not set.

Fixes bug 1131994

Change-Id: I454d9df736edd771f9d5d93eca4cd317116cc985
Merge remote-tracking branch 'm_src_repo/webob-issue' into build-temp