[TBTablesTest] Add an initialization method: setupTestDB().

Recently, the way to setup DBs for a test has been increaesed
and complicated. Especially, current tests have  to include lines to
initializes DBs.

This patch is the first step to solve the problem.
Hereafter all tests using DBs basically call setupTestDB() in
cut_setup(). Then they call loadTestDBxxxx() if needed.