virtualisation.docker: require docker.service for docker-prune.service

else docker-prune fails when docker is not launched. Adjusted the test as well

Changed files
+3
nixos
modules
virtualisation
tests
+2
nixos/modules/virtualisation/docker.nix
···
'';
startAt = optional cfg.autoPrune.enable cfg.autoPrune.dates;
+
after = [ "docker.service" ];
+
requires = [ "docker.service" ];
};
assertions = [
+1
nixos/tests/docker.nix
···
{ pkgs, ... }:
{
virtualisation.docker.enable = true;
+
virtualisation.docker.autoPrune.enable = true;
virtualisation.docker.package = pkgs.docker;
users.users = {