The Linux NFSv4.1/4.2 client now uses the CLAIM_DELEG_CUR_FH
variant of the Open operation when delegations are recalled and
the client has a local open of the file.  This patch adds
support for this variant of Open to the NFSv4.1/4.2 server.

This patch only affects mounts from Linux clients when delegations
are enabled on the server.

MFC after:	2 weeks