Make sure there is no listener left on port 6667 after teardown

src/jable/db.clj

@@ -185,6 +185,7 @@
     (teardown! [_ test node]
       (info node "tearing down Sable")
       (cu/stop-daemon! "sable_ircd" pidfile)
+      (c/exec "killall" "listener_process" :|| "true")  ; not always shut down properly
       (c/exec "rm" "-f"
               "/var/log/sable_ircd.log"
               (map (fn [file] (str "/usr/local/bin/" file)) sable_binaries))