Fix "caddy-frontend: Support not resolving backend hostnames"

There was missing updates in the test itself.

Fixes 14d90bcd
5 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
passed SlapOS.Eggs.UnitTest-Master.Python2

00:09:49

passed SlapOS.Eggs.UnitTest-Master.Python3

00:10:56

failed SlapOS.SlapRunner.ResilienceTest-Master.ERP5

00:52:50

failed SlapOS.SoftwareReleases.IntegrationTest-Master.Python2

04:34:08

failed SlapOS.SoftwareReleases.IntegrationTest-Master.Python3

06:00:47