[BUG] The rocketmq 4.9.6 still use 'free' to get system memory

[kizuna-lek]

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BUG REPORT

1. Please describe the issue you observed:

• What did you do (The steps to reproduce)?
  get Rocketmq 4.9.6 from docker hub: https://hub.docker.com/r/apache/rocketmq/tags?name=4.9.6

• What did you expect to see?
  In calculate_heap_sizes function, get system memory from cgroup or env

• What did you see instead?
  get system memory from 'free' cmd