target/pscsi: Don't leak scsi_host if hba is VIRTUAL_HOST

target/pscsi: Don't leak scsi_host if hba is VIRTUAL_HOST

commit 5a7125c64def3b21f8147eca8b54949a60963942 upstream.

See https://bugzilla.redhat.com/show_bug.cgi?id=1025672

We need to put() the reference to the scsi host that we got in
pscsi_configure_device(). In VIRTUAL_HOST mode it is associated with
the dev_virt, not the hba_virt.

Signed-off-by: Andy Grover <agrover@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>