qemu-iotests: Test blockdev-backup in 055 This applies cases on drive-backup on blockdev-backup, except cases with target format and mode. Also add a case to check source == target. Signed-off-by: Fam Zheng <famz@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> Message-id: 1418899027-8445-5-git-send-email-famz@redhat.com Signed-off-by: Max Reitz <mreitz@redhat.com>