ipaldap: merge external_bind into LDAPClient

* Rename do_external_bind to external_bind
* Remove user_name argument in  external_bind() and always set it
    to effective user name

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

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

ipaserver/plugins/ldap2.py

@@ -28,7 +28,6 @@ Backend plugin for LDAP.
 # everything except the CrudBackend methods, where dn is part of the entry dict.
 
 import os
-import pwd
 
 import ldap as _ldap
 
@@ -181,9 +180,7 @@ class ldap2(CrudBackend, LDAPClient):
                                client_controls=clientctrls)
         elif autobind != AUTOBIND_DISABLED and os.getegid() == 0 and ldapi:
             try:
-                pw_name = pwd.getpwuid(os.geteuid()).pw_name
-                client.external_bind(pw_name,
-                                     server_controls=serverctrls,
+                client.external_bind(server_controls=serverctrls,
                                      client_controls=clientctrls)
             except errors.NotFound:
                 if autobind == AUTOBIND_ENABLED: