ad-auth: sssd: Allow forcing a particular DC

ad-auth/templates/sssd.conf.j2

@@ -32,3 +32,6 @@ ad_gpo_access_control = disabled
 ldap_search_base = {{ authbase }}?subtree?(&(!(objectClass=computer))(!(userAccountControl:1.2.840.113556.1.4.803:=2)))
 {% endif %}
 dyndns_update=false
+{% if ad_auth_renew_force_dc is defined %}
+ad_server = {{ ad_auth_renew_force_dc }}
+{% endif %}