core: Fix dao tests not to print lookup error

Although this does not break tests, seeing an exception
when running the first test in a bunch of tests is not something nice.
This patch solve this by introducing an EJBUtilsStrategy that uses the
createDataSource static method to "lookup" the dataSource, and set it
before DbFacadadeLocator.getDbFacade is called.

Change-Id: I9f37acaea5c21463c4e126799524a3c41b6071a3
Signed-off-by: Yair Zaslavsky <yzaslavs@redhat.com>