The error path for blocklayout's device lookup is missing a reference drop
for the case where a lookup finds the device, but the device is marked with
NFS_DEVICEID_UNAVAILABLE.
Fixes: b3dce6a2f060 ("pnfs/blocklayout: handle transient devices") Signed-off-by: Benjamin Coddington <bcodding@redhat.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>