upgrade: treat duplicate entry when updating as not an error

When we attempt to update an entry during upgrade, it may have already
contain the data in question between the check and the update. Ignore
the change in this case and record it in the log.

Fixes: https://pagure.io/freeipa/issue/7450
Reviewed-By: Christian Heimes <cheimes@redhat.com>

ipaserver/install/ldapupdate.py

@@ -21,6 +21,7 @@
 
 # TODO
 # save undo files?
+from __future__ import absolute_import
 
 import base64
 import logging
@@ -849,6 +850,9 @@ def _update_record(self, update):
             except errors.DatabaseError as e:
                 logger.error("Update failed: %s", e)
                 updated = False
+            except errors.DuplicateEntry as e:
+                logger.debug("Update already exists, skip it: %s", e)
+                updated = False
             except errors.ACIError as e:
                 logger.error("Update failed: %s", e)
                 updated = False