Revert "erp5.mariadb: Create no test database by default."

This reverts commit 37a0e975d2d001e5e6d26eaa20efd9464abe5960.

It was too early to change this default value, code requesting test
instance is not ready for this yet, which in turn prevents latest SR
improvements from being tested. Break the cycle by creating test databases
again. This code will go away again in the future.