BE/IPA/AD/LDAP: Initialize the refresh callback from a list to reduce logic duplication
Related: https://pagure.io/SSSD/sssd/issue/4012
This patch slightly increases the line count, but on the other hand the
code is now more declarative and contains less logic, which should
hopefully decrease the maintenance cost in the future.
Reviewed-by: Sumit Bose <sbose@redhat.com>