[8.19] (backport #18525) Stop tests from polluting maven settings

[mergify]

Release notes

[rn:skip]

What does this PR do?

The pluginmanager tests modify ~/.m2/settings.xml. Previously when that file exists it would be restored on test cleanup. However if that file did not exist prior to the tests, the file with nonsense values generated during testing would persist. This would cause subsequent issues when the pluginmanager or other systems that respect those maven settings. This commit updates the test to ensure the test file is deleted if it did not previously exist.

Previously any developer who run the tests locally and did not have an existing ~/.m2/settings.xml would get a file with nonsense proxies which would break the pluginmanager's ability to download jar dependencies of gems.

NOTE: Fortunately this did not affect logstash artifact creation because we do testing/packaging on separate hosts.

How to test this PR locally

# Ensure ~/.m2/settings.xml is empty or has "real" config in it
cat ~/.m2/settings.xml
# run tests 
./gradlew rubyTests
# Ensure settings.xml is the same (or does not exist if it did not previously). 
cat ~/.m2/settings.xml

Logs

Previously the tests would leave behing a file like:

<settings xmlns="http://maven.apache.org/SETTINGS/1.0.0"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0
  https://maven.apache.org/xsd/settings-1.0.0.xsd">
  <proxies>
    
    <proxy>
      <id>local.dev.0</id>
      <active>true</active>
      <protocol>http</protocol>
      <host>local.dev</host>
      <port>9898</port>
      <username>a</username>
      <password>b</password>
    </proxy>
  
    <proxy>
      <id>local.dev.1</id>
      <active>true</active>
      <protocol>https</protocol>
      <host>local.dev</host>
      <port>9898</port>
      <username>c</username>
      <password>d</password>
    </proxy>
  
  </proxies>
</settings>

This would cause issues with the pluginmanager when jar-dependencies need to dowload jars for gem installation. Unfortunately that is masked because of retry logic (the jar is failed to be downlaoded but the rest of the gem code is, so on the second retry the pluginmanager thinks the complete gem has been installed).

---

This is an automatic backport of pull request #18525 done by Mergify.

[github-actions]

🤖 GitHub comments

Just comment with:

• run docs-build : Re-trigger the docs validation. (use unformatted text in the comment!)
• /run exhaustive tests : Run the exhaustive tests Buildkite pipeline.

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: c7fea3a

cc @donoghuc

[mergify]

This pull request has not been merged yet. Could you please review and merge it @donoghuc? 🙏