HDDS-14890. Improve ozone_add_default_gc_opts

[AdyChechani]

What changes were proposed in this pull request?

• Made java_major_version a local variable so it doesn’t leak into the broader shell environment.
• GC options now go into a local variable. Passing XX as the checkstring takes care of duplicate options, so there’s no need for the old [[ ! "$OZONE_OPTS" =~ "-XX" ]] check.
• Removed ozone_error messages, instead used ozone_debug.

What is the link to the Apache JIRA

https://issues.apache.org/jira/browse/HDDS-14890

How was this patch tested?

Tested the function ozone_add_default_gc_opts in isolation manually by creating a shell script locally, verifying that:

• Default GC options are correctly appended to OZONE_OPTS
• No duplicate -XX options are added when one is already present

[adoroszlai]

Thanks @AdyChechani for the patch.

[adoroszlai]

Please remove these ozone_debug messages. Since presence of -XX is not checked beforehand, these would always be printed. ozone_add_param already prints debug message:

ozone/hadoop-ozone/dist/src/shell/ozone/ozone-functions.sh

Lines 1137 to 1139 in 644a018

	ozone_debug "$1 accepted $3"
	else
	ozone_debug "$1 declined $3"

[adoroszlai]

nit: please move this variable assignment into the if block to avoid running it unnecessarily for client commands

[adoroszlai]

Thanks @AdyChechani for updating the patch.

[adoroszlai]

@AdyChechani Please try to avoid force-push when updating the PR. Here are some great articles that explain why:

https://developers.mattermost.com/blog/submitting-great-prs/#4-avoid-force-pushing
https://www.freecodecamp.org/news/optimize-pull-requests-for-reviewer-happiness#request-a-review