openafs.spec: Use /etc/openafs for configuration files

Previous commits uses a directory /etc/sysconfig/openafs instead of
/etc/openafs, which is in line with how Debian packages are built.  In
an attempt to keep things similar to debian, use /etc/openafs/ for
client configuration, and /etc/openafs/server/ for server
configuration.

Compatibility links are updated to reflect this change.