block: iotest - update 084 to test static VDI image creation

This updates the VDI corruption test to also test static VDI image
creation, as well as the default dynamic image creation.

Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Jeff Cody <jcody@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
