nfsd: allow SC_STATUS_FREEABLE when searching via nfs4_lookup_stateid()

The pynfs DELEG8 test fails when run against nfsd. It acquires a
delegation and then lets the lease time out. It then tries to use the
deleg stateid and expects to see NFS4ERR_DELEG_REVOKED, but it gets
bad NFS4ERR_BAD_STATEID instead.

When a delegation is revoked, it's initially marked with
SC_STATUS_REVOKED, or SC_STATUS_ADMIN_REVOKED and later, it's marked
with the SC_STATUS_FREEABLE flag, which denotes that it is waiting for
s FREE_STATEID call.

nfs4_lookup_stateid() accepts a statusmask that includes the status
flags that a found stateid is allowed to have. Currently, that mask
never includes SC_STATUS_FREEABLE, which means that revoked delegations
are (almost) never found.

Add SC_STATUS_FREEABLE to the always-allowed status flags, and remove it
from nfsd4_delegreturn() since it's now always implied.

Fixes: 8dd91e8d ("nfsd: fix race between laundromat and free_stateid")
Cc: stable@vger.kernel.org
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>