[OpenAFS] GiveUpAllCallBacks callers

[Harald Barth]

> The version information per rxdebug is unreliable, of course. It's any
> arbitrary build-time string.

Yes. I mess around it in my builds for this site, but I suspect that
most people are sensible and restrict the messing around to appending
subversions, like

$ rxdebug jack 7000 -v
Trying 130.237.232.202 (port 7000):
AFS version:  OpenAFS 1.4.12-pdc59 built  2010-04-07 

> An RPC with a version vector or something more reliable than a text
> string has already been discussed
> and is presumably going to be in the offing.

So the options for introducing the GiveUpAllCallBacks are:

a) Wait for the version vector RPC
b) Do something with the version string in the meantime
c) Just state that 1.4.5 is "too old" to bother
d) The GetStatistics64 RPC trick

Even if I as time goes more and more tend to c), the b) or a) options
give the client a chance to nag about upgrading if such servers are
still out there.

Harald.