Follow-up to the following commits:
abdc5961c3: Fix starting the firewall
e090701e2d: Order before sysinit
Solely use sysinit.target here instead of multi-user.target because we
want to make sure that the iptables rules are applied *before* any
socket units are started.
The reason I've dropped the wantedBy on multi-user.target is that
sysinit.target is already a part of the dependency chain of
multi-user.target.
To make sure that this holds true, I've added a small test case to
ensure that during switch of the configuration the firewall.service is
considered as well.
Tested using the firewall NixOS test.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
Cc: @edolstra
fb46df8a9a