dns: check if container exists using ldapi

Previously an adhoc connection was established for checking if
dns(sec) container exists. A simple or external bind was used.
Instead, always connect with ldapi through api.Backend.ldap2.

https://fedorahosted.org/freeipa/ticket/6461

Reviewed-By: Martin Babinsky <mbabinsk@redhat.com>
Reviewed-By: Martin Basti <mbasti@redhat.com>

ipaserver/install/server/replicainstall.py

@@ -171,9 +171,7 @@ def install_http(config, auto_redirect, ca_is_configured, ca_file,
 def install_dns_records(config, options, remote_api):
 
     if not bindinstance.dns_container_exists(
-            config.host_name,
-            ipautil.realm_to_suffix(config.realm_name),
-            realm=config.realm_name, ldapi=True):
+            ipautil.realm_to_suffix(config.realm_name)):
         return
 
     try: