nfsd41: refactor nfs4_open_deleg_none_ext logic out of nfs4_open_delegation

When a 4.1 client asks for a delegation and the server returns none
op_delegate_type is set to NFS4_OPEN_DELEGATE_NONE_EXT
and op_why_no_deleg is set to either WND4_CONTENTION or WND4_RESOURCE.
Or, if the client sent a NFS4_SHARE_WANT_CANCEL (which it is not supposed
to ever do until our server supports delegations signaling),
op_why_no_deleg is set to WND4_CANCELLED.

Note that for WND4_CONTENTION and WND4_RESOURCE, the xdr layer is hard coded
at this time to encode boolean FALSE for ond_server_will_push_deleg /
ond_server_will_signal_avail.

Signed-off-by: Benny Halevy <bhalevy@tonian.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>