py3: open temporary ldif file in text mode

ldif parser uses file in text mode, so we have to open it in text mode
in py3

Also values passed to parser should be bytes

https://fedorahosted.org/freeipa/ticket/4985

Reviewed-By: Christian Heimes <cheimes@redhat.com>
Reviewed-By: Jan Cholasta <jcholast@redhat.com>

ipaserver/install/dsinstance.py

@@ -587,14 +587,15 @@ class DsInstance(service.Service):
             'dse.ldif'
         )
 
-        with tempfile.NamedTemporaryFile(delete=False) as new_dse_ldif:
+        with tempfile.NamedTemporaryFile(
+                mode='w', delete=False) as new_dse_ldif:
             temp_filename = new_dse_ldif.name
             with open(dse_filename, "r") as input_file:
                 parser = installutils.ModifyLDIF(input_file, new_dse_ldif)
                 parser.replace_value(
                         'cn=config,cn=ldbm database,cn=plugins,cn=config',
                         'nsslapd-db-locks',
-                        ['50000']
+                        [b'50000']
                         )
                 if self.config_ldif:
                     # parse modifications from ldif file supplied by the admin