nfs no longer reconnects for udp sockets

[Sam Leffler]

Alfred Perlstein wrote:
> Hey guys, someone was having issues with NFS mounts and
> I happened to notice that it appears that the
> "reconnect if socket went south" semantics I added a few
> years ago were basically disabled by the nfs optimizations
> added for "recv side processing".
>
> The problem is as such:
>
> You have an NFS mount on UDP.
> Somehow the route goes bad.
> The UDP socket is now "broken" as the route will remain
> hosed forever.  This is particularly bad when an interface
> flaps and loses its IP address as the UDP socket's route is
> then set to nul or loopback or something and never gets fixed.
> Your nfs mount goes dead even if the routing issues is
> resolved (interface brought back up).
>
> Please see attached patch.
>
> Easy way to reproduce problem:
>
> mount an nfs filesystem using UDP.
> ifconfig interface down
> try to access mount
> ifconfig interface up
> mount should still be dead.
>
> Please review.
>   

This patch doesn't apply against HEAD.  There are also gratuitous style 
changes.   Looks fine, but please re-spin (and test against HEAD).

    Sam