libafs: don't crash on no addresses in afs_Conn

libafs: don't crash on no addresses in afs_Conn

we try to avoid a crash on a missing serverHost; do the same
on missing addrs in that host

FIXES 130714

Change-Id: Ic6bab8654cf7bf85351a9482b9ba5d51e5a768d5
Reviewed-on: http://gerrit.openafs.org/7287
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Derrick Brashear <shadow@dementix.org>