NFS: Request a directory delegation on ACCESS, CREATE, and UNLINK

NFS: Request a directory delegation on ACCESS, CREATE, and UNLINK

This patch adds a new flag: NFS_INO_REQ_DIR_DELEG to signal that a
directory wants to request a directory delegation the next time it does
a GETATTR. I have the client request a directory delegation when doing
an access, create, or unlink call since these calls indicate that a user
is working with a directory.

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