kvm: use "auto=1" in the url and backend-url

This avoids duplication of information.
19 jobs for gitlab-upgrade in 0 seconds
Status Job ID Name Coverage
  External
passed SlapOS.SlapRunner.ResilienceTest-Master

00:24:08

failed SlapOS.SlapRunner.ResilienceTest-Master.ERP5

00:14:26

failed SlapOS.SoftwareReleases.IntegrationTest-Master

07:20:10

passed SlapOS.SlapRunner.ResilienceTest-Master

00:24:23

passed SlapOS.SlapRunner.ResilienceTest-Master

00:24:28

passed SlapOS.SlapRunner.ResilienceTest-Master

00:25:20

passed SlapOS.SlapRunner.ResilienceTest-Master

00:24:25

passed SlapOS.SlapRunner.ResilienceTest-Master

00:25:08

passed SlapOS.SlapRunner.ResilienceTest-Master

00:24:25

failed SlapOS.SlapRunner.ResilienceTest-Master.ERP5

00:12:17

failed SlapOS.SlapRunner.ResilienceTest-Master.ERP5

00:18:49

failed SlapOS.SlapRunner.ResilienceTest-Master.ERP5

00:14:38

failed SlapOS.SlapRunner.ResilienceTest-Master.ERP5

00:16:09

failed SlapOS.SlapRunner.ResilienceTest-Master.ERP5

00:13:20

failed SlapOS.SlapRunner.ResilienceTest-Master.ERP5

00:13:24

failed SlapOS.SlapRunner.ResilienceTest-Master.ERP5

00:13:10

failed SlapOS.SoftwareReleases.IntegrationTest-Master

05:13:30

failed SlapOS.SoftwareReleases.IntegrationTest-Master

05:37:45

failed SlapOS.SoftwareReleases.IntegrationTest-Master

06:58:10