Preserving the 'x-fowarded-proto' headers

Compare:

**https** https://mf-chsdi3.dev.bgdi.ch/mom_https_getcap/1.0.0/WMTSCapabilities.xml

with

**http** http://mf-chsdi3.dev.bgdi.ch/mom_https_getcap/1.0.0/WMTSCapabilities.xml