Fix shared reference between the two load reports (#450)

This shared reference caused the resource usages between the current report (not published to ZooKeeper) and the
most recently written report to be incorrect and hence when the broker utilization was rapidly changing (e.g., after
a broker restart), the load report only got written once per 15 minutes.

pulsar-broker/src/main/java/com/yahoo/pulsar/broker/LocalBrokerData.java

@@ -116,11 +116,18 @@ public class LocalBrokerData extends JSONWritable implements ServiceLookupData {
     // Set the cpu, memory, and direct memory to that of the new system resource
     // usage data.
     private void updateSystemResourceUsage(final SystemResourceUsage systemResourceUsage) {
-        this.cpu = systemResourceUsage.cpu;
-        this.memory = systemResourceUsage.memory;
-        this.directMemory = systemResourceUsage.directMemory;
-        this.bandwidthIn = systemResourceUsage.bandwidthIn;
-        this.bandwidthOut = systemResourceUsage.bandwidthOut;
+        updateSystemResourceUsage(systemResourceUsage.cpu, systemResourceUsage.memory, systemResourceUsage.directMemory,
+                systemResourceUsage.bandwidthIn, systemResourceUsage.bandwidthOut);
+    }
+
+    // Update resource usage given each individual usage.
+    private void updateSystemResourceUsage(final ResourceUsage cpu, final ResourceUsage memory,
+            final ResourceUsage directMemory, final ResourceUsage bandwidthIn, final ResourceUsage bandwidthOut) {
+        this.cpu = new ResourceUsage(cpu);
+        this.memory = new ResourceUsage(memory);
+        this.directMemory = new ResourceUsage(directMemory);
+        this.bandwidthIn = new ResourceUsage(bandwidthIn);
+        this.bandwidthOut = new ResourceUsage(bandwidthOut);
     }
 
     // Aggregate all message, throughput, topic count, bundle count, consumer

pulsar-common/src/main/java/com/yahoo/pulsar/common/policies/data/loadbalancer/ResourceUsage.java

@@ -28,8 +28,12 @@ public class ResourceUsage {
         this.limit = limit;
     }
 
-    public ResourceUsage() {
+    public ResourceUsage(ResourceUsage that) {
+        this.usage = that.usage;
+        this.limit = that.limit;
+    }
 
+    public ResourceUsage() {
     }
 
     public void reset() {