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

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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