[OpenAFS] 1.8.0: Cache inconsistent after vos release

[Harald Barth]

We see problems when doing a vos release that the 1.8.0 clients "miss"
that the ro volume has changed. We think this is repeatable.

Our setup is:

* server version OpenAFS 1.6.22 2017-12-07 
  Centos
* client version OpenAFS 1.8.0  2018-05-08
  Both on Centos and Ubuntu 

As it works with older AFS _clients_ and the same server, we suspect
that this is a 1.8.0 issue. An fs flushv fixes it.

I am not aware of any firewalls or NAT between server and client.

Before digging deeper: Has anyone of you seen this as well? If not,
you might want to test this if you think about moving to 1.8 or
already have.

Thanks,
Harald.