kvm: Bang immediately in case of vnc_promise problem

There is no reason to wait before banging the partition if VNC is not
available, as reprocessing is the only way to fix the situation.
7 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
passed SlapOS.Eggs.UnitTest-Master.Python2

00:10:13

passed SlapOS.Eggs.UnitTest-Master.Python3

00:11:39

passed SlapOS.SlapRunner.ResilienceTest-Master

00:21:48

failed SlapOS.SlapRunner.ResilienceTest-Master.ERP5

00:21:40

failed SlapOS.SoftwareReleases.IntegrationTest-Master.Python2

22:28:10

failed SlapOS.SoftwareReleases.IntegrationTest-Master.Python3

04:22:29

passed Wendelin.StandaloneDeploymentScriptTest-Debian.Buster.Master

12:06:05