[ROCKETMQ-37] Polish log output information in MQClientManager, closes...

[ROCKETMQ-37] Polish log output information in MQClientManager, closes apache/incubator-rocketmq#33, closes apache/incubator-rocketmq#26

broker/src/main/java/org/apache/rocketmq/broker/subscription/SubscriptionGroupManager.java

@@ -184,7 +184,7 @@ public class SubscriptionGroupManager extends ConfigManager {
             this.dataVersion.nextVersion();
             this.persist();
         } else {
-            log.warn("delete subscription group failed, subscription group: {} not exist", old);
+            log.warn("delete subscription group failed, subscription groupName: {} not exist", groupName);
         }
     }
 }

client/src/main/java/org/apache/rocketmq/client/impl/MQClientManager.java

@@ -53,8 +53,9 @@ public class MQClientManager {
             MQClientInstance prev = this.factoryTable.putIfAbsent(clientId, instance);
             if (prev != null) {
                 instance = prev;
+                log.warn("Returned Previous MQClientInstance for clientId:[{}]", clientId);
             } else {
-                log.warn("Previous MQClientInstance has created for clientId:[{}]", clientId);
+                log.info("Created new MQClientInstance for clientId:[{}]", clientId);
             }
         }