fix: httpc connection close #714

Job	Run time
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/http3/admin)	10m 57s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/plugin/[a-k]*)	10m 52s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/plugin/[l-z]*)	10m 50s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/admin t/cli t/config-center-yaml...	10m 57s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/node t/pubsub t/router t/script ...	10m 58s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/http3/admin)	10m 58s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/plugin/[a-k]*)	10m 57s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/plugin/[l-z]*)	10m 56s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/admin t/cli t/config-center-yaml t/cont...	10m 56s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/node t/pubsub t/router t/script t/secre...	10m 59s
	1h 49m 20s

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