流控功能默认将health接口排除流控范围

#### 背景
servicecomb的qps-flowcontrol-provider提供了针对于服务粒度和接口粒度的流控配置，当超过流控阈值后，接口会调度失败，servicecomb默认的health接口一般用于检测服务当前状态
#### 问题
当health接口触发流控后，可能导致误判将对应服务实例下线导致流量受损等情况

#### 诉求
服务开启流控功能后，health接口默认不参与全局流控值的计算，此时health流控不会对当前高负载场景有所缓解，且触发实例下线后会加剧流量承载压力

Start by tracing the qps-flowcontrol-provider handling for service and interface-level limits, then locate how the default health interface is processed. Confirm the intended behavior with the existing issue discussion and verify that health requests no longer contribute to global flow-control calculations while normal interfaces retain their limits.

Written by the indexing model from the issue text.