LP#1447746: Fix lp957466_update_date_and_source regression test

LP#1447746: Fix lp957466_update_date_and_source regression test

The new code introduced through LP1447746 adding an update_bib_source flag to
Vandelay merge profiles broke a test that was verifying the bib source and
edit fields were updated in Vandelay uploads.

This patch fixes the test and also adds a new test to ensure the flag works as
expected when set to both true and false. It also renames the test since the
it's now testing the newer code rather than the previous expected behavior.

Signed-off-by: Kathy Lussier <klussier@masslnc.org>
Signed-off-by: Ben Shum <ben@evergreener.net>