fixing "umount -f" for the NFS client

[Rick Macklem]

Mark Felder wrote:
> On Thu, Aug 29, 2013, at 7:50, Rick Macklem wrote:
> > 
> > Finally, neither of these options are safe to use for NFSv4,
> > because
> > operations that manipulate state (like locks) cannot be safely
> > interrupted,
> > since they will leave the lock in an undefined state, at least for
> > the
> > FreeBSD server.
> > So, at least for NFSv4, a forced dismount is a necessary
> > alternative.
> > 
> 
> I was not aware of this specific issue, so thank you for the warning
> 
Yeah. It's documented in the BUGS section of "man mount_nfs" and few
(me included;-) can be bothered reading an entire man page.

rick