There were accidentally two disks with 'vdc' target with corresponding
blockjobs which made libvirt leak some references as there are not
supposed to be two blockjobs for a single disk. Fix this mess by
renaming some of the disks.

In addition the block job names also didn't correspond to the naming
convetion which also includes the disk target. Fix it as well.
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>
ACKed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NMartin Kletzander <mkletzan@redhat.com>