Avoid unnecessary timezone conversion (#354)

[edwinwzhe]

• fixes avoid unnecessary timezone conversion when use_numpy=True #354

Checklist:

• Add tests that demonstrate the correct behavior of the change. Tests should fail without the change.
• Add or update relevant docs, in the docs folder and in code.
• Ensure PR doesn't contain untouched code reformatting: spaces, etc.
• Run flake8 and fix issues.
• Run pytest no tests failed. See https://clickhouse-driver.readthedocs.io/en/latest/development.html.

[coveralls]

Coverage: 96.341% (+0.001%) from 96.34% when pulling 0373bc8 on edwinwzhe:avoid_unnecessary_tz_conversion into f27e772 on mymarilyn:master.