fix flaky test of PredictionITTests and RestConnectorToolIT

[Hailong-am]

Description

1. Add per-defined cluster setting to disable MLSyncUpJob for JVM private OpenSearch Cluster, so that it will not create .plugin-ml-config index automatically every 10 seconds.
2. Skip RestConnectorToolIT if AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY are not set
3. Add retry for creating connector if ML encryption master key has not been initialized yet

Issues Resolved

#2436

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed per the DCO using --signoff

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[ylwu-amzn]

@Hailong-am Can you rebase with main branch and check if IT can pass?

[ylwu-amzn]

Add per-defined cluster setting to disable MLSyncUpJob for JVM private OpenSearch Cluster, so that it will not create .plugin-ml-config index automatically every 10 seconds.

This seems a code bug. Can you confirm this is just impacting IT ?

[ylwu-amzn]

Approve to unblock falied IT for 2.15 release

[opensearch-trigger-bot]

The backport to 2.x failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-2.x 2.x
# Navigate to the new working tree
cd .worktrees/backport-2.x
# Create a new branch
git switch --create backport/backport-2437-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 f28bb740e87cd520190b003011303d5a85d477d6
# Push it to GitHub
git push --set-upstream origin backport/backport-2437-to-2.x
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-2.x

Then, create a pull request where the base branch is 2.x and the compare/head branch is backport/backport-2437-to-2.x.

[opensearch-trigger-bot]

The backport to 2.15 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-2.15 2.15
# Navigate to the new working tree
cd .worktrees/backport-2.15
# Create a new branch
git switch --create backport/backport-2437-to-2.15
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 f28bb740e87cd520190b003011303d5a85d477d6
# Push it to GitHub
git push --set-upstream origin backport/backport-2437-to-2.15
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-2.15

Then, create a pull request where the base branch is 2.15 and the compare/head branch is backport/backport-2437-to-2.15.