more work on install scripts

mullvad-vpn-daemon/mullvad-vpn-daemon.post-upgrade

@@ -0,0 +1,8 @@
+#!/usr/bin/env bash
+set -eu
+
+echo "mullvad post-upgrade"
+
+# Overwrite the cached relay list with the one embedded in the package.
+mkdir /var/cache/mullvad-vpn
+cp /usr/share/mullvad-vpn/relays.json /var/cache/mullvad-vpn/relays.json