We need to re-initialize the pacman keyring for every machine,
otherwise every machine would have the same pacman master key. The same
pacman master key opens the possibility for Mitm-attacks.

Signed-off-by: Christian Rebischke <Chris.Rebischke@posteo.de>

The rankmirrors tool is not part of the official arch linux ISO
anymore.. Furthermore I don't think it has so much effect

This commit fixes the 'file not found: `fsck.btrfs''-Error during
system upgrade.

added polkit to pacstrap for systemctl poweroff, added sudo to poweroff
command, moved link for systemd-resolved to postinstall.sh

added new postinstall.sh, moved the controllers to postinstall.sh and added the script to vagrant.json