bug: 重新选主时 namespace controller goroutine没有正常退出

[wangzhenfei-tal]

Current Behavior

环境： k8s v1.28.5
描述： controller重新选主时 namespace controller goroutine没有正常退出，导致内存泄漏

PR: #2412

Expected Behavior

No response

Error Logs

No response

Steps to Reproduce

1. 安装apisix ingress controller
2. 删除apisix ingress controller 申请的租约 ，直至触发主从切换。
3. 通过pprof （ /debug/pprof/goroutine?debug=1 ）观察到每重复一次步骤2，goroutine总数就会增加2。同时内存有少量增长。

Environment

• APISIX Ingress controller version (run apisix-ingress-controller version --long)
• Kubernetes cluster version (run kubectl version)
• OS version if running APISIX Ingress controller in a bare-metal environment (run uname -a)