nixos/acme: Add proper nginx/httpd config reload checks

Testing of certs failed randomly when the web server was still
returning old certs even after the reload was "complete". This was
because the reload commands send process signals and do not wait
for the worker processes to restart. This commit adds log watchers
which wait for the worker processes to be restarted.

nixos/modules/services/web-servers/apache-httpd/default.nix

@@ -795,7 +795,7 @@ in
         Type = "oneshot";
         TimeoutSec = 60;
         ExecCondition = "/run/current-system/systemd/bin/systemctl -q is-active httpd.service";
-        ExecStartPre = "${pkg}/bin/apachectl configtest";
+        ExecStartPre = "${pkg}/bin/httpd -f ${httpdConf} -t";
         ExecStart = "/run/current-system/systemd/bin/systemctl reload httpd.service";
       };
     };