playbook: chmod 666 /dev/net/tun also

It seems some machines don't have the default 666 permission on
/dev/net/tun so we force it in the playbook.

Also add names to the tasks.
4 jobs for imt
Status Job ID Name Coverage
  External
passed ERP5.StandaloneDeploymentScriptTest-Debian.Buster

passed SlapOS-Master.StandaloneDeploymentScriptTest-Debian.Bullseye

passed Wendelin.StandaloneDeploymentScriptTest-Debian.Bullseye

passed Wendelin.StandaloneDeploymentScriptTest-Debian.Buster