Add OPEN claim type NFS4_OPEN_CLAIM_DELEGATE_CUR to nfsd4_open().

A delegation stateid and a name are provided.  OPEN with O_CREAT is not legal
with this claim type; otherwise, use the NFS4_OPEN_CLAIM_NULL code path to
lookup the filename to be opened.
Signed-off-by: Andy Adamson <andros@citi.umich.edu>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>