test_backup_restore: do not fail on missing KrbLastSuccessfulAuth

Since FreeIPA 4.5.1 now sets 'Disable last successful auth' option by
default (see https://pagure.io/freeipa/issue/5313), the
'KrbLastSuccessfulAuth' may not always be present on the user entry. The
restored entry checker in backup/restore suite should consider this.

https://pagure.io/freeipa/issue/6956

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

ipatests/test_integration/test_backup_and_restore.py

@@ -58,7 +58,7 @@ def check_admin_in_ldap(host):
     assert entry.dn == user_dn
     assert entry['uid'] == ['admin']
 
-    del entry['krbLastSuccessfulAuth']
+    entry.pop('krbLastSuccessfulAuth', None)
 
     return entry