[8.15] Fix memory limit check bytes to GB conversion (backport #13838)

[mergify]

Motivation/summary

This PR closed the issue #13837, by fixing the bytes to GB conversion in the fallback memory check.

Checklist

Update CHANGELOG.asciidoc

• Documentation has been updated

For functional changes, consider:

• Is it observable through the addition of either logging or metrics?
• Is its use being published in telemetry to enable product improvement?
• Have system tests been added to avoid regression?

How to test these changes

The easiest way to test this change is to create a custom cgroup with a memory limit that is larger than the total system memory, then start apm-server binary with the created cgroup. Observer APM Server logs for "cgroup memory limit exceed available memory, falling back to the total system memory".

cgcreate  -g memory:apm_test
cgget -r memory.limit_in_bytes=10737418240 /apm_test
cgexec -g memory:apm_test ./apm-server run

Related issues

Changelog

==== Bug fixes

• Fix memory limit fallback check bytes to GB conversion {pull}13838[13838]

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  This is an automatic backport of pull request Fix memory limit check bytes to GB conversion #13838 done by Mergify.