Update pr9885: update global config description

Author: weizhouapache

framework/cluster/src/main/java/com/cloud/cluster/ClusterManager.java

@@ -27,9 +27,9 @@
 public interface ClusterManager extends Manager {
     static final String ALERT_SUBJECT = "cluster-alert";
     final ConfigKey<Integer> HeartbeatInterval = new ConfigKey<Integer>(Integer.class, "cluster.heartbeat.interval", "management-server", "1500",
-        "Interval to check for the heart beat between management server nodes", false);
+        "Interval (in milliseconds) to check for the heart beat between management server nodes", false);
     final ConfigKey<Integer> HeartbeatThreshold = new ConfigKey<Integer>(Integer.class, "cluster.heartbeat.threshold", "management-server", "150000",
-        "Threshold before self-fence the management server", true);
+        "Threshold (in milliseconds) before self-fence the management server. The threshold should be larger than management.server.stats.interval", true);
 
     /**
      * Adds a new packet to the incoming queue.