This patch fills the DriveInfo->unit after hotplugging a scsi disk.
It makes a difference when auto-assigning a scsi id, where unit was
left filled with '-1' instead of the actual scsi id.
With this patch applied the the drive naming logic in drive_init() works
as good as it did in previous releases. Which means it works fine with
a single scsi bus.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>