budb: Fail if afsconf_GetExtendedCellInfo does

Rather than silently ignoring the failure of
afsconf_GetExtendedCellInfo, and then using garbage cell
configuration, just fail to start if afsconf can't parse the
config directory.

Reviewed-on: http://gerrit.openafs.org/9247
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit 3fbdc609dc025cfcaac6949485d6fb072bf34764)

Change-Id: I40f0aefda1bc44ce92a7733ec644002229c32079
Reviewed-on: http://gerrit.openafs.org/9536
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>