auth: refactor afsconf_Open
Move code to check the AFSCONF environment variable and read the
.AFSCONF files to separate functions.
Rename the internal functions afsconf_OpenInternal and
afsconf_CloseInternal to the more aptly named LoadConfig and
UnloadConfig in preparation for other changes. Add doxygen comments for
these functions.
Change-Id: Ie3361036c59c9e6ef99801891fff9fad63840344
Reviewed-on: https://gerrit.openafs.org/13397
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>