在集群环境下存在问题，不会进行joinGroup

贡献一个bug，多tm，tc集群环境下：
a,b两个服务，a调b，各自完成业务，提交事务。
在非集群环境下，调用情况如下：
createGroup
joinGroup
notifyGroup
notifyUnit
remove group
notify group successfully
集群环境下调用情况如下：
createGroup
notifyGroup
notifyUnit
remove group
notify group successfully
集群环境b服务没有进行joinGroup，导致其事务不会提交，a正常完成，数据不一致

Start by reproducing the non-cluster and cluster call sequences described in the issue, then trace the cluster path to find where b skips joinGroup. Done means the participating service joins the group and its transaction commits consistently with a, without data inconsistency.

Scritto dal modello di indicizzazione a partire dal testo della issue.