ERP5TypeLiveTestCase: repair running live tests from zope

This fixes a regression with 445e8fa8 (ERP5TypeTestCase: rework
default manager password generation, 2024-05-27), it was no longer
possible to run live tests from a "normal" zope instance, this was
failing with:

Traceback (most recent call last):
  File "./eggs/Zope-5.10-py3.9.egg/Testing/ZopeTestCase/PortalTestCase.py", line 59, in setUp
    self._setup()
  File "./parts/erp5/product/ERP5Type/tests/ERP5TypeLiveTestCase.py", line 156, in _setup
    self.login()
  File "./parts/erp5/product/ERP5Type/tests/ERP5TypeTestCase.py", line 290, in login
    return PortalTestCase.login(self, user_name)
  File "./eggs/Zope-5.10-py3.9.egg/Testing/ZopeTestCase/PortalTestCase.py", line 146, in login
    user = user.__of__(uf)
AttributeError: 'NoneType' object has no attribute '__of__'

It was only possible from a runUnitTest instance.
43 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
passed ERP5.CodingStyleTest-Master

02:00:13

failed ERP5.PerformanceTest-Master

00:35:08

failed ERP5.UnitTest-Master

04:40:00

passed SlapOS.Eggs.UnitTest-Master.Python2

00:42:18

passed SlapOS.Eggs.UnitTest-Master.Python3

00:30:10

passed Wendelin.UnitTest-Master

01:10:47

passed ERP5.CodingStyleTest-Master

02:38:19

passed ERP5.CodingStyleTest-Master

01:58:49

passed ERP5.CodingStyleTest-Master

01:34:14

passed ERP5.CodingStyleTest-Master

01:47:38

passed ERP5.CodingStyleTest-Master

02:23:23

passed ERP5.CodingStyleTest-Master

05:44:24

failed ERP5.PerformanceTest-Master

04:10:39

failed ERP5.PerformanceTest-Master

00:35:24

failed ERP5.UnitTest-Master

09:22:47

failed ERP5.UnitTest-Master

08:35:37

failed ERP5.UnitTest-Master

04:53:42

failed ERP5.UnitTest-Master

04:09:08

passed SlapOS.Eggs.UnitTest-Master.Python2

00:43:49

passed SlapOS.Eggs.UnitTest-Master.Python2

00:36:18

passed SlapOS.Eggs.UnitTest-Master.Python2

00:23:05

passed SlapOS.Eggs.UnitTest-Master.Python2

00:25:41

passed SlapOS.Eggs.UnitTest-Master.Python2

00:27:06

passed SlapOS.Eggs.UnitTest-Master.Python2

00:41:01

passed SlapOS.Eggs.UnitTest-Master.Python2

00:39:24

passed SlapOS.Eggs.UnitTest-Master.Python2

00:37:16

passed SlapOS.Eggs.UnitTest-Master.Python3

00:24:47

passed SlapOS.Eggs.UnitTest-Master.Python3

00:47:53

passed SlapOS.Eggs.UnitTest-Master.Python3

00:41:17

passed SlapOS.Eggs.UnitTest-Master.Python3

01:55:59

passed SlapOS.Eggs.UnitTest-Master.Python3

00:24:00

passed SlapOS.Eggs.UnitTest-Master.Python3

00:41:25

passed SlapOS.Eggs.UnitTest-Master.Python3

00:40:43

passed SlapOS.Eggs.UnitTest-Master.Python3

00:45:48

passed Wendelin.UnitTest-Master

00:42:42

passed Wendelin.UnitTest-Master

00:49:42

passed Wendelin.UnitTest-Master

00:50:19

passed Wendelin.UnitTest-Master

00:52:40

failed Wendelin.UnitTest-Master

00:47:11

failed Wendelin.UnitTest-Master

02:28:13

failed Wendelin.UnitTest-Master

01:03:16

passed Wendelin.UnitTest-Master

00:54:15

failed Wendelin.UnitTest-Master

01:09:05