qa_crowbarsetup: allow arbitrary cloud names
improve #39 with a snippet from @tboerger
mkcloud: include $cloud in LV name

this allows to run multiple clouds in a single large VG
to take advantage of IO going to different backend disks
mkcloud: distribute cloud lvm volumes over all physical devices

In order to distribute the disk IO we distribute the volumes over all
PVs of the lvm upon creation. This is useful for setups with multiple
disks.