software/erp5/test: fix flaky test_activity_processing

wait a first time that ERP5 have finished processing activities for
initial site creation and tolerate that during this time zopes might
reply with error code
11 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
passed Cloudooo.UnitTest-Master

00:09:30

passed SlapOS.Eggs.UnitTest-Master.Python2

00:12:03

passed SlapOS.Eggs.UnitTest-Master.Python3

00:11:01

passed SlapOS.SlapRunner.ResilienceTest-Master

00:23:35

failed SlapOS.SlapRunner.ResilienceTest-Master.ERP5

01:41:04

failed SlapOS.SoftwareReleases.IntegrationTest-Master.Python2

failed SlapOS.SoftwareReleases.IntegrationTest-Master.Python3

20:29:08

passed Wendelin.StandaloneDeploymentScriptTest-Debian.Buster.Master

09:05:40

failed SlapOS.SoftwareReleases.IntegrationTest-Master.Python2

04:27:32

failed SlapOS.SoftwareReleases.IntegrationTest-Master.Python2

passed Wendelin.StandaloneDeploymentScriptTest-Debian.Buster.Master

08:29:30