ldap2: modify arguments for create_connection

* Remove unused and obsolete function arguments:
    * tls_certfile
    * tls_keyfile
    * debug_level
* Rename tls_cacertfile to cacert (same as name in LDAPClient)
* Set cacert to constants.CACERT by default.

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

Reviewed-By: Martin Basti <mbasti@redhat.com>
Reviewed-By: Jan Cholasta <jcholast@redhat.com>

ipaserver/plugins/migration.py

@@ -890,19 +890,19 @@ migration process might be incomplete\n''')
 
         cacert = None
         if options.get('cacertfile') is not None:
-            #store CA cert into file
+            # store CA cert into file
             tmp_ca_cert_f = write_tmp_file(options['cacertfile'])
             cacert = tmp_ca_cert_f.name
 
-            #start TLS connection
+            # start TLS connection
             ds_ldap.connect(bind_dn=options['binddn'], bind_pw=bindpw,
-                tls_cacertfile=cacert)
+                            cacert=cacert)
 
             tmp_ca_cert_f.close()
         else:
             ds_ldap.connect(bind_dn=options['binddn'], bind_pw=bindpw)
 
-        #check whether the compat plugin is enabled
+        # check whether the compat plugin is enabled
         if not options.get('compat'):
             try:
                 ldap.get_entry(DN(('cn', 'compat'), (api.env.basedn)))