NFSD: Handle layout stid in nfsd4_drop_revoked_stid()

NFSD: Handle layout stid in nfsd4_drop_revoked_stid()

nfsd4_drop_revoked_stid() has no SC_TYPE_LAYOUT case, so when a
client sends FREE_STATEID for an admin-revoked layout stid, the
default branch releases cl_lock and returns without unhashing or
releasing the stid.  The stid remains in the IDR and on the
per-client list until the client is destroyed.

Remove the layout stid from the per-client list and call
nfs4_put_stid() to drop the creation reference.  When the
refcount reaches zero, nfsd4_free_layout_stateid() handles the
remaining cleanup: cancelling the fence worker, removing from
the per-file list, and freeing the slab object.

Fixes: 1e33e1414bec ("nfsd: allow layout state to be admin-revoked.")
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Tested-by: Dai Ngo <dai.ngo@oracle.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>