caddy-frontend: Rename test to follow real check

The test name (and shared instance name) was misleading.
15 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
passed Cloudooo.UnitTest-Master

00:09:43

passed SlapOS.Eggs.UnitTest-Master.Python2

00:11:34

passed SlapOS.Eggs.UnitTest-Master.Python3

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passed SlapOS.SlapRunner.ResilienceTest-Master

00:22:00

failed SlapOS.SlapRunner.ResilienceTest-Master.ERP5

01:28:45

passed SlapOS.SoftwareReleases.IntegrationTest-Master.Python2

22:08:55

failed SlapOS.SoftwareReleases.IntegrationTest-Master.Python3

20:29:10

passed Wendelin.StandaloneDeploymentScriptTest-Debian.Buster.Master

08:24:12

passed SlapOS.Eggs.UnitTest-Master.Python2

00:21:42

passed SlapOS.Eggs.UnitTest-Master.Python2

00:11:49

passed SlapOS.Eggs.UnitTest-Master.Python3

00:12:28

passed SlapOS.Eggs.UnitTest-Master.Python3

00:12:36

passed SlapOS.SlapRunner.ResilienceTest-Master

00:22:24

passed SlapOS.SlapRunner.ResilienceTest-Master

00:21:45

failed SlapOS.SlapRunner.ResilienceTest-Master.ERP5

01:29:13