Seleniumserver: set slot quantity as an instance parameter

See merge request !1336
20 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
passed Cloudooo.UnitTest-Master

00:13:46

passed ERP5.StandaloneDeploymentScriptTest-Debian.Buster

00:37:38

failed ERP5.StandaloneDeploymentScriptTest-Debian.Buster.Master

15:02:14

passed SlapOS.Eggs.UnitTest-Master.Python2

00:29:43

passed SlapOS.Eggs.UnitTest-Master.Python3

00:26:54

passed SlapOS.Eggs.UnitTest-Master.Python3Next

00:28:48

failed SlapOS.SoftwareReleases.IntegrationTest-Master

08:52:41

passed SlapOS.Theia.ResilienceTest-Master-ERP5

08:56:35

passed SlapOS.Theia.ResilienceTest-Master-Gitlab

14:53:25

failed Wendelin.StandaloneDeploymentScriptTest-Debian.Buster

14:46:11

passed Wendelin.StandaloneDeploymentScriptTest-Debian.Buster.Master

11:04:13

failed Wendelin.UnitTest-Master-Py3

00:36:50

failed Zodbtools.UnitTest-Master.ZODB6.Python3

00:56:37

passed ERP5.StandaloneDeploymentScriptTest-Debian.Buster

00:40:46

passed SlapOS.Eggs.UnitTest-Master.Python2

00:29:58

passed SlapOS.Eggs.UnitTest-Master.Python3

00:43:14

failed SlapOS.Eggs.UnitTest-Master.Python3Next

00:54:21

passed SlapOS.Eggs.UnitTest-Master.Python3Next

00:51:33

passed SlapOS.SoftwareReleases.IntegrationTest-Master

08:15:36

passed Wendelin.StandaloneDeploymentScriptTest-Debian.Buster.Master

11:54:39