After introducing codes for updating sqlalchemy version 2,
when db is populated to postgresql by running `tacker-db-manage
upgrade head`, `sqlalchemy.table` function raise "NoSuchTable"
error if "engine" is passed as autoload_with.
This patch fix the above error by changing "engine" to "connection".
Closes-bug: #2085879
Change-Id: If14d101ceb510b38d14725ae27b81d9131cd4332