route: avoid overlapping strcpy

Passing overlapping buffers to strcpy yields an undefined result, so
let's avoid it. The copy doesn't really need to happen anyways, we can
just point to the domain part of the hostname.

This was discovered with _FORTIFY_SOURCE.

Sponsored by: Klara, Inc.
Sponsored by: Stormshield
Reviewed by: allanjude, emaste, imp, melifaro (all previous version)

(cherry picked from commit 158f319428c10143ce2ffe766416207c75578931)