Remove bottlenecks in process handling, still some rough edges

cluster/cluster.go

@@ -634,7 +634,6 @@ func (c *cluster) Shutdown() error {
 
 	if c.manager != nil {
 		c.manager.NodesClear()
-		c.manager = nil
 	}
 
 	if c.api != nil {
@@ -648,6 +647,9 @@ func (c *cluster) Shutdown() error {
 		c.raft.Shutdown()
 	}
 
+	c.manager = nil
+	c.raft = nil
+
 	return nil
 }