Revert "cache last heartbeat list in memory"

This reverts commit 87678ea92d.

server/user-monitor-list.js

@@ -4,36 +4,14 @@
 class UserMonitorList {
     list = {};
 
-    /**
-     * Add or update
-     * @param userID
-     * @param monitor
-     */
     add(userID, monitor) {
         if (! this.list[userID]) {
             this.list[userID] = {};
         }
-
-        // Stopped the old monitor if same id
-        this.stop(userID, monitor.id);
-
         this.list[userID][monitor.id] = monitor;
     }
 
-    stop(userID, monitorID) {
-        if (this.list[userID][monitorID]) {
-            let oldMonitor = this.list[userID][monitorID];
-
-            if (oldMonitor) {
-                oldMonitor.stop();
-            } else {
-                console.log("No old monitor: " + monitorID);
-            }
-        }
-    }
-
     delete(userID, monitorID) {
-        this.stop(userID, monitorID);
         let monitorList = this.getMonitorList(userID);
         delete monitorList[monitorID];
     }