add test for create_backup

*add positive test and corresponding client for server
action: createBackup.
*verify that create backup successfully and rotate
backups correctly.
*add the property prefix filter support in image_list_detail
of the image service client, because the image api in nova can't
support sort_dir='asc' and sort_key='created_at'.
so we can submit request like the following to get specified images

GET /images/detail?sort_key=created_at&property-image_type=backup

Change-Id: I43337970e4b1b71c7290416c517a8f93152b168f
Merge "add test for create_backup"