Cleaning up vgone.

[Don Lewis]

On 10 Mar, Matthew Dillon wrote:

>     Another thing I did in DragonFly was to get rid of the crazy handling of
>     the vnode's reference count during the reclaim.  I don't know what
>     FreeBSD-HEAD is doing now, but FreeBSD-4 dropped the ref count to 0
>     and then did the crazy VXLOCK stuff.  In DragonFly I changed that so
>     the ref count is left at 1 (not 0) during the reclaim.  This required
>     fixing up a few cases that were checking the refcount against an absolute
>     0 or 1 (I forget the cases), but it made the code a whole lot easier to
>     understand.

I suggested doing this a long time ago, but there seemed to be enough
side effects that I didn't try to implement it.