slaprunner: fix publishing of custom-frontend-url

3 jobs for 1.0
Status Job ID Name Coverage
  External
failed SlapOS.SoftwareReleases.IntegrationTest-Master

04:22:54

failed SlapOS.SoftwareReleases.IntegrationTest-Master

failed SlapOS.SoftwareReleases.IntegrationTest-Master

05:19:17