NFSv4: Fix OPEN_DOWNGRADE error handling

If OPEN_DOWNGRADE returns a state error, then we want to initiate
state recovery in addition to marking the stateid as closed.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>