execute fencecommand in seq for kvm, as there are only 5 default nio reading work threads on kvm agent. pinganswer may not be got serviced immediately, then agent will reconnect to mgt server again and again

agent/src/com/cloud/agent/Agent.java

@@ -607,6 +607,8 @@ public class Agent implements HandlerFactory, IAgentControl {
 
             try {
                 task.getLink().send(request.toBytes());
+                //if i can send pingcommand out, means the link is ok
+                setLastPingResponseTime();
             } catch (final ClosedChannelException e) {
                 s_logger.warn("Unable to send request: " + request.toString());
             }

api/src/com/cloud/agent/api/FenceCommand.java

@@ -29,12 +29,18 @@ public class FenceCommand extends Command {
     String vmName;
     String hostGuid;
     String hostIp;
+    boolean inSeq;
     
     public FenceCommand(VirtualMachine vm, Host host) {
         super();
         vmName = vm.getInstanceName();
         hostGuid = host.getGuid();
         hostIp = host.getPrivateIpAddress();
+        inSeq = false;
+    }
+    
+    public void setSeq(boolean inseq) {
+    	inSeq = inseq;
     }
     
     public String getVmName() {
@@ -51,6 +57,6 @@ public class FenceCommand extends Command {
 
     @Override
     public boolean executeInSequence() {
-        return false;
+        return inSeq;
     }
 }

server/src/com/cloud/ha/KVMFencer.java

@@ -84,6 +84,7 @@ public class KVMFencer implements FenceBuilder {
 
 		List<HostVO> hosts = _hostDao.listByCluster(host.getClusterId());
 		FenceCommand fence = new FenceCommand(vm, host);
+		fence.setSeq(true);
 
 		for (HostVO h : hosts) {
 			if (h.getHypervisorType() == HypervisorType.KVM) {