Return correct value from getAutoCommit

[findepi]

Fixes #657

[github-actions]

Benchmark                           (client)  (statement)   Mode  Cnt     Score     Error  Units
Basic.insertOneRandomNumber  clickhouse-jdbc       normal  thrpt   20   271.963 ±  27.842  ops/s
Basic.insertOneRandomNumber  clickhouse-jdbc     prepared  thrpt   20   264.666 ±  29.205  ops/s
Basic.selectOneRandomNumber  clickhouse-jdbc       normal  thrpt   20  1331.424 ± 159.869  ops/s
Basic.selectOneRandomNumber  clickhouse-jdbc     prepared  thrpt   20  1389.874 ± 161.367  ops/s

[zhicwu]

Thank you @findepi for fixing the issue.

[findepi]

Thanks for a quick merge!