7.0 workaround oca issue 22

This attempts to work around OCA issue 22, "AssertionError: 0 worker found in database instead of 1". After I encountered this problem in a second installation, I decided to create a pull request. I don't know what causes the assertion to fail (probably some timing issue or a problem with starting Odoo and the connector with too few workers), but it makes the connector work again for the two installations.