Fix: Report correct listen URL to client.

The URL is constructed considering Protocol, TLS Mode, Host, and Port.

This considers:
 - The Host:-header as provided by the client,
 - The effective listensocket of the client,
 - Global configuration.

This works for:
 - Playlist generation,
 - Admin authed playlist generation,
 - Stats based XSLT.

It also unifies code:
 - Default stats values.

Not yet included:
 - YP requests.
1 job from ph3-listen-sockets in 44 seconds (queued for 2 minutes and 20 seconds)
Status Job ID Name Coverage
passed #283
docker alpine