libadmin: Don't try to release garbage connection

In bos_ServerOpen, initalise the contents of bos_server structure
to 0 using calloc, so that if we jump to the error handling stuff
before they are assigned real values we don't end up trying to
release garbage.

Reviewed-on: http://gerrit.openafs.org/9163
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
(cherry picked from commit 17154a3c0afa88f7bb25e2b642fc13ee69c2b7db)

Change-Id: Iaa6e5166cb29799feb82ca29ef3e78ceea82d6e2
Reviewed-on: http://gerrit.openafs.org/9524
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>