logstash: fix support for multiple plugin paths

nixos/modules/services/logging/logstash.nix

@@ -4,13 +4,9 @@ with lib;
 
 let
   cfg = config.services.logstash;
-  pluginPath = lib.concatStringsSep ":" cfg.plugins;
-  havePluginPath = lib.length cfg.plugins > 0;
   ops = lib.optionalString;
   verbosityFlag = "--log.level " + cfg.logLevel;
 
-  pluginsPath = "--path.plugins ${pluginPath}";
-
   logstashConf = pkgs.writeText "logstash.conf" ''
     input {
       ${cfg.inputConfig}
@@ -173,7 +169,7 @@ in
         ExecStart = concatStringsSep " " (filter (s: stringLength s != 0) [
           "${cfg.package}/bin/logstash"
           "-w ${toString cfg.filterWorkers}"
-          (ops havePluginPath pluginsPath)
+          (concatMapStringsSep " " (x: "--path.plugins ${x}") cfg.plugins)
           "${verbosityFlag}"
           "-f ${logstashConf}"
           "--path.settings ${logstashSettingsDir}"