caddy-frontend: Follow up slapos.core changes

Since da03653908aea9a62f805faf0328f7b2f046abaa slapos.core's slapproxy transmit
more parameters, so adapt tests to account for it.
2 jobs for 1.0
Status Job ID Name Coverage
  External
failed SlapOS.SoftwareReleases.IntegrationTest-Master.Python2

passed SlapOS.SoftwareReleases.IntegrationTest-Master.Python3