Unix CM: Log reason for marking server up or down

Unix CM: Log reason for marking server up or down

When we mark a server up or down also log the error code that says
why we did so, for help in debugging connection issues.

Reviewed-on: http://gerrit.openafs.org/6116
Reviewed-by: Jeffrey Altman <jaltman@secure-endpoints.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>
Tested-by: Derrick Brashear <shadow@dementix.org>
(cherry picked from commit 33526acb56c1794838c6a8c02e9b8f5022a04ac1)

Change-Id: If0318faf99f2a7582c93f74f3fc210c0c02fbaf7
Reviewed-on: http://gerrit.openafs.org/8001
Reviewed-by: Derrick Brashear <shadow@dementix.org>
Tested-by: BuildBot <buildbot@rampaginggeek.com>