kauth: Don't ignore GetExtendedCellInfo failures

Don't ignore a failure from afsconf_GetExtendedCellInfo, as it will
leave buffers that we later read uninitialised.

Caught by clang-analyzer

Change-Id: Ia0c2675a3083385d011fd340f36bf13373f89feb
Reviewed-on: http://gerrit.openafs.org/9180
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>