tests(*): remove useless strategy arg from reload_kong helper function

[windmgc]

Summary

This PR removes an useless strategy argument from one the helpers function reload_kong, as well as another related function wait_until_no_common_workers.

This argument(and the reload_kong function itself) was made a helpers function in PR #8670 (see the diff here, which used to be a local helper function inside a test case. The argument strategy was only for sleeping a bit more time when the test was running under a Cassandra deployment and there was no other use besides this.

This argument was removed in EE earlier in another PR https://github.com/Kong/kong-ee/pull/3420, in commit https://github.com/Kong/kong-ee/commit/28850266ee35f7bc4f37d0b53edade4a39aabd55, but it was not removed in CE and caused divergence between the helpers function since then.

After the investigation, I see no meaning for us to keep this argument any longer, so I created this PR to totally remove it from CE test suites and to keep a consistent function signature between CE/EE repo.

NOTE: there is no need to cherry-pick this PR to EE, or to say my expectation is cherry-picking will create an empty commit

Checklist

• The Pull Request has tests
• A changelog file has been created under changelog/unreleased/kong or skip-changelog label added on PR if changelog is unnecessary. README.md
• There is a user-facing docs PR against https://github.com/Kong/docs.konghq.com - PUT DOCS PR HERE

Issue reference

https://konghq.atlassian.net/browse/FTI-5922

[team-gateway-bot]

Cherry-pick failed for master, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally.

git remote add upstream https://github.com/kong/kong-ee
git fetch upstream master
git worktree add -d .worktree/cherry-pick-13980-to-master-to-upstream upstream/master
cd .worktree/cherry-pick-13980-to-master-to-upstream
git checkout -b cherry-pick-13980-to-master-to-upstream
ancref=$(git merge-base 9b2e13395b15276ceeb4604870f37ce3228fe08c c062faffe50856a65e1bd89e825d1e04e80cfb4e)
git cherry-pick -x $ancref..c062faffe50856a65e1bd89e825d1e04e80cfb4e