caddy-frontend: Expose node id in the statistic

Otherwise it's almost impossible to check for which node statistics are shown.
4 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
passed SlapOS.SlapRunner.ResilienceTest-Master

00:27:17

failed SlapOS.SlapRunner.ResilienceTest-Master.ERP5

01:56:03

failed SlapOS.SoftwareReleases.IntegrationTest-Master.Python2

05:42:47

failed SlapOS.SoftwareReleases.IntegrationTest-Master.Python3

03:56:41