"Move" NM connectivity check file to a subdomain

The file should not be on the main domain as it adds unnecessary complexity to the archweb role and there is a bigger chance that we unintentionally break connectivity checking (which has happened in the past[1][2]).

This doesn't remove the file from the main domain[3], as we need to ship a updated NetworkManager package first.

[1] https://www.reddit.com/r/archlinux/comments/keai0g/does_anyone_know_if_this_is_normal/ [2] https://www.reddit.com/r/gnome/comments/ke9ytm/network_manager_popup/ [3] http://www.archlinux.org/check_network_status.txt

Fix #239 (closed)