Fix Flaky tests

After the MR acknowledge transactions after committed to WAL got merged, we are observing some flaky tests.

Failed tests:

• https://gitlab.com/gitlab-org/gitaly/-/jobs/8672768407#L327
• https://gitlab.com/gitlab-org/gitaly/-/jobs/8674064810#L328

Flaky tests related to transaction-manager

• https://gitlab.com/gitlab-org/gitaly/-/jobs/8674064763#L288
• https://gitlab.com/gitlab-org/gitaly/-/jobs/8674064765#L327
• https://gitlab.com/gitlab-org/gitaly/-/jobs/8672162535#L764
• https://gitlab.com/gitlab-org/gitaly/-/jobs/8674821747#L328
• https://gitlab.com/gitlab-org/gitaly/-/jobs/8675050393#L288