FlowPropertyListener中的configUpdate需要优化

FlowPropertyListener中方法已经使用了synchronized，FlowRuleUtil.buildFlowRuleMap(value); 是否还有必要返回ConcurrentHashMap？。
并且flowRules是hashMap。在方法中被莫名其妙的替换成了ConcurrentHashMap类型。

Locate FlowPropertyListener and inspect configUpdate, including its synchronized scope and the call to FlowRuleUtil.buildFlowRuleMap(value). Trace how flowRules changes between HashMap and ConcurrentHashMap, then verify the intended map type and concurrency behavior with the relevant existing tests.

Written by the indexing model from the issue text.