auth: prevent uninitialized key list in AFS config

_afsconf_OpenInternal() may exit early for a number of reasons
before properly initalizing afsconf_dir->listKeys.
This leads to a crash when _afsconf_CloseInternal() attempts
to clean up listKeys.

Prevent this situation by calling afsconf_InitKeys() before any
possible exit from _afsconf_OpenInternal().

Change-Id: I6911427817a2518a576c00a7ea56351f9fb4fd19
Reviewed-on: http://gerrit.openafs.org/10323
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>