nixos/lighttpd: add reload support

Allow reloading the webserver, which is useful when e.g there are new
certificates available that we want lighttpd to use, but don't want to
completely shut down the server.

nixos/tests/lighttpd.nix

@@ -17,5 +17,6 @@ import ./make-test-python.nix ({ lib, pkgs, ... }: {
     server.wait_for_unit("lighttpd.service")
     res = server.succeed("curl --fail http://localhost/file.txt")
     assert "hello nixos test" in res, f"bad server response: '{res}'"
+    server.succeed("systemctl reload lighttpd")
   '';
 })