removed a forgotten debugging print

Signed-off-by: Jan Dvořák <mordae@anilinux.org>
implemented MockManager.rows

Signed-off-by: Jan Dvořák <mordae@anilinux.org>
improve test failure output

Signed-off-by: Jan Dvořák <mordae@anilinux.org>
change storage_pool placement semantics

We now place storage_pool along with all it's disks on every host that
can at least partially access it.

Signed-off-by: Jan Dvořák <mordae@anilinux.org>