MFC 210136:

MFC 210136:
Retire the NFS access cache timestamp structure.  It was used in VOP_OPEN()
to avoid sending multiple ACCESS/GETATTR RPCs during a single open()
between VOP_LOOKUP() and VOP_OPEN().  Now we always send the RPC in
VOP_LOOKUP() and not VOP_OPEN() in the cases that multiple RPCs could be
sent.

To preserve the ABI I have left the structure in place, but renamed it
to 'n_unused' and just removed the code that updates it.

git-svn-id: svn://svn.freebsd.org/base/stable/8@210888 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f