Fix the issue that tiflash's data is not clean up (#768)

We use ServicePort in DestroyClusterTombstone to construct id and filter by id,
but the id of instances of cluster is contract using Port(TCPPort for
	tiflash),
so it will not get the instance and clean it's data in DestroyClusterTombstone.

Note the GetMainPort() is TCPPort now, change the code to both
using GetMainPort() to avoid inconsistent.

pkg/cluster/operation/action.go

@@ -222,6 +222,7 @@ func DestroyClusterTombstone(
 		}
 
 		instances := (&spec.TiFlashComponent{Specification: cluster}).Instances()
+		id = s.Host + ":" + strconv.Itoa(s.GetMainPort())
 		instances = filterID(instances, id)
 
 		err = StopComponent(getter, instances, options.OptTimeout)

pkg/cluster/spec/tiflash.go

@@ -107,7 +107,7 @@ func (c *TiFlashComponent) Instances() []Instance {
 			InstanceSpec: s,
 			Name:         c.Name(),
 			Host:         s.Host,
-			Port:         s.TCPPort,
+			Port:         s.GetMainPort(),
 			SSHP:         s.SSHPort,
 
 			Ports: []int{