passing db connection name to methods of DB. runned in my application.

Signed-off-by: kanonji <kanonji@users.noreply.github.com>
fixed because it looks like to be corrected by following other. But have not been runned even once

Signed-off-by: kanonji <kanonji@users.noreply.github.com>
Merge pull request #1769 from kanonji/fix_passing_arg_in_dbutil

Fix passing db connection name to methods of DB class in dbutil