erp5_core: setup a random id generator on portal_callable

If one callable has the default ID '1', it will break nearly all newContent calls on empty object
19 jobs for for_testrunner_3 in 0 seconds
Status Job ID Name Coverage
  External
failed ERP5.UnitTest-Master

01:11:16

passed SlapOS.Eggs.UnitTest-Master.Python2

00:09:29

passed SlapOS.Eggs.UnitTest-Master.Python3

00:11:32

failed ERP5.UnitTest-Master

01:19:28

failed ERP5.UnitTest-Master

01:18:19

failed ERP5.UnitTest-Master

01:21:27

failed ERP5.UnitTest-Master

04:24:36

passed SlapOS.Eggs.UnitTest-Master.Python2

00:13:15

passed SlapOS.Eggs.UnitTest-Master.Python2

00:10:35

passed SlapOS.Eggs.UnitTest-Master.Python2

00:09:36

passed SlapOS.Eggs.UnitTest-Master.Python2

00:10:28

passed SlapOS.Eggs.UnitTest-Master.Python2

00:21:23

passed SlapOS.Eggs.UnitTest-Master.Python2

00:10:13

passed SlapOS.Eggs.UnitTest-Master.Python3

00:22:21

passed SlapOS.Eggs.UnitTest-Master.Python3

00:22:32

passed SlapOS.Eggs.UnitTest-Master.Python3

00:14:08

passed SlapOS.Eggs.UnitTest-Master.Python3

00:35:07

passed SlapOS.Eggs.UnitTest-Master.Python3

00:10:23

passed SlapOS.Eggs.UnitTest-Master.Python3

00:10:32