Remove connection from pool before waiting for results

[vgvoleg]

Pull request type

Please check the type of change your PR introduces:

• [x] Bugfix
• [ ] Feature
• [ ] Code style update (formatting, renaming)
• [ ] Refactoring (no functional changes, no api changes)
• [ ] Build related changes
• [ ] Documentation content changes
• [ ] Other (please describe):

What is the current behavior?

Issue Number: N/A

What is the new behavior?

Other information

[github-actions[bot]]

:volcano: Here are results of SLO test for Python SDK over Query Service:

Grafana Dashboard

[github-actions[bot]]

:volcano: Here are results of SLO test for Python SDK over Table Service:

Grafana Dashboard