[Swan] an xauth logging message

[D. Hugh Redelmeier]

| From: Paul Wouters <paul at nohats.ca>

| On Fri, 1 Mar 2013, D. Hugh Redelmeier wrote:
| 
| > Are xauth_server and xauth_client mutually exclusive?
| > Are modecfg_server and modecfg_client mutually exclusive?
| 
| Yes both are mutually exclusive. but the two are now. That is,
| you can be an xauth server but a modecfg_client (it is called
| pull or push mode but that term too is confusing when you think
| that initiator/responder can flip around as well)

Having two mutually exclusive boolean variables (or fields) is usually
useless redundancy:
- it makes the code longer
- it creates new ways to have bugs
- it doesn't increase the chances of a bug being caught.

This is in contrast with useful redundancy.  That actually does
increase the chance of a bug being caught.  For example, parity or ECC
in RAM.

passert is a tool for turning useless redundancy into useful
redundancy.  But getting rid of this redundancy would be better.

So: I propose that you get rid of one of each pair.  Probably *_client
because !server reads a little better to me than !client.  Of course
this can be put off until there is spare time.