[Dubbo-3657] Fix junit test failed (#3658)

Author: maoyiz

dubbo-monitor/dubbo-monitor-api/src/main/java/org/apache/dubbo/monitor/support/AbstractMonitorFactory.java

@@ -85,8 +85,8 @@ public Monitor getMonitor(URL url) {
 
             final URL monitorUrl = url;
             final CompletableFuture<Monitor> completableFuture = CompletableFuture.supplyAsync(() -> AbstractMonitorFactory.this.createMonitor(monitorUrl));
-            completableFuture.thenRunAsync(new MonitorListener(key), executor);
             FUTURES.put(key, completableFuture);
+            completableFuture.thenRunAsync(new MonitorListener(key), executor);
 
             return null;
         } finally {

dubbo-monitor/dubbo-monitor-default/src/test/java/org/apache/dubbo/monitor/dubbo/DubboMonitorTest.java

@@ -61,7 +61,7 @@ public Class<MonitorService> getInterface() {
         }
 
         public URL getUrl() {
-            return URL.valueOf("dubbo://127.0.0.1:7070?interval=20");
+            return URL.valueOf("dubbo://127.0.0.1:7070?interval=1000");
         }
 
         @Override