health check can't use

[wanzhenhan]

环境：
version: v1.4.0
路由和upstream配置：

curl -i --connect-timeout 1 http://127.0.0.1:9080/apisix/admin/routes/4444 -H 'X-API-KEY: edd1c9f034335f136f87ad84b625c8f1' -X PUT -d '
{
    "methods": ["POST", "GET","DELETE"],
    "uri": "/xxxx/v1/readiness",
    "plugins": {
    },
    "upstream": {
        "type": "roundrobin",
        "nodes": {
            "10.82.4.112:10188": 1,
            "10.82.4.112:10190": 1
        },
        "checks": {
            "active": {
                "http_path": "/xxxx/v1/liveness",
                "host": "health.com",
                "healthy": {
                    "interval": 4,
                    "successes": 1
                },
                "unhealthy": {
                    "interval": 5,
                    "http_failures": 1
                }
            }
        }
    }
}'

当客户端发起访问时，报如下错误：
failed to run balancer_by_lua*: /usr/local/openresty/lualib/resty/lock.lua:153: API disabled in the context of balancer_by_lua*

[membphis]

Is it an inevitable bug, or does it happen occasionally?

Do you have a way to reproduce this bug stably?

[membphis]

@wanzhenhan please make a try with this PR: #1971

I think this bug has been fixed.