NFSv4: Fix a reboot recovery race when opening a file

If the server reboots after it has replied to our OPEN, but before we
call nfs4_opendata_to_nfs4_state(), then the reboot recovery thread
will not see a stateid for this open, and so will fail to recover it.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>