caddy-frontend: Solve ATS configuration asymmetry

Accessing http with path starting with /HTTPS/ would result with 503 responses
from ATS itself.

Test is covering the problem and also asserting that fix does not damage https
access with path starting with /HTTP/
1 job for fix/caddy-frontend-ats-remap-assymetry in 0 seconds
Status Job ID Name Coverage
  External
passed SlapOS.SoftwareReleases.IntegrationTest-luke/fix/caddy-frontend-ats-remap-assymetry

02:37:40