升级ServiceComb，从1.3升级到2.7.5的过程中遇到了一个问题

对某个循环调用同一个服务器端的客户端接口进行多次调用[不算很频繁]，wait response会不断增长，直到30s后超时，然后会慢慢发生熔断
陆续出现code=408;msg=CommonExceptionData [message=Request Timeout.]
接着出现InvocationException: InvocationException: code=500;msg=CommonExceptionData [message=No available address found.]
查看调用链之后发现，耗时在wait response上面。
请问是因为从从1.3升级到2.7.5从而某些参数变更出现的问题吗？
客户端与服务器的配置如下：

```
servicecomb:
accesslog:
enabled: true
pattern: "%t %p %m %H %U %s %b %D"
server:
http2:
useAlpnEnabled: false
rest:
client:
http2:
enabled: false
connection:
maxPoolSize: 50
```

Start with the reported wait-response timing and the supplied servicecomb.rest.client.connection.maxPoolSize and HTTP/2 settings, then compare behavior between versions 1.3 and 2.7.5 under repeated calls to one server. Reproduce the 30-second timeout and subsequent circuit breaking, and use the call-chain data to identify whether a configuration change or regression causes the delay; done means the cause and corrective change are documented.

Written by the indexing model from the issue text.