Make volumes appear as SCSI devices in aarch64

Make volumes appear as SCSI devices in aarch64

Adding volumes in openstack by default uses virtio_blk and the
devices appear as /dev/vdX. In aarch64 however a qemu pci slot
is already in use so the tests cannot assign more than one volume
to a VM. Forcing the drives to use virtio-scsi solves the issue
and allows more volumes to be attached as /dev/sdX. The variable
defining the drive is VOLUME_DEVICE_NAME and is passed as
environmental variable when the container is created.

JIRA: ARMBAND-376

Change-Id: Ia688cff338ff319e22a3b26796fa197297c23ce0
Signed-off-by: Charalampos Kominos <Charalampos.Kominos@enea.com>