perf(ssl): reuse array length variable (#11053) #2

Job	Run time
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/http3/admin)	11m 1s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/plugin/[a-k]*)	24m 53s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/plugin/[l-z]*)	23m 47s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/admin t/cli t/config-center-yaml...	21m 49s
build (ubuntu-20.04, linux_openresty, lua-resty-worker-events, t/node t/pubsub t/router t/script ...	22m 8s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/http3/admin)	13m 22s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/plugin/[a-k]*)	24m 30s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/plugin/[l-z]*)	24m 7s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/admin t/cli t/config-center-yaml t/cont...	23m 3s
build (ubuntu-20.04, linux_openresty, lua-resty-events, t/node t/pubsub t/router t/script t/secre...	22m 42s
	3h 31m 22s

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