caddy-frontend/test: Introduce HttpFrontendTestCase

This allows to test the minimal setup of the configuration.

The setup is split, as slaves are now not required.

Some test methods are changed to reflect the reality of instantiation.
7 jobs for cloudooo_upgrade_dependency in 0 seconds
Status Job ID Name Coverage
  External
passed SlapOS.SlapRunner.ResilienceTest-Master

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failed SlapOS.SlapRunner.ResilienceTest-Master.ERP5

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failed SlapOS.SoftwareReleases.IntegrationTest-Jerome-WIP.own-distributor

failed SlapOS.SoftwareReleases.IntegrationTest-Master.Python2

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failed SlapOS.SoftwareReleases.IntegrationTest-Master.Python3

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failed SlapOS.SoftwareReleases.IntegrationTest-Master.Python2

failed SlapOS.SoftwareReleases.IntegrationTest-Master.Python3

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