Tweaking code to find default location of the database

It turns out that this bit of code was correct, but hopefully now it's clearer.

It's still pretty confusing where this is set, and in what priority.
(eg. the .rmgrc config file). I'm not sure why the prior one seems to work in other places
Add work_in_progress decorator for currently failing Unit Tests

This is a proof (test) of concept. If it works, then we should add this
decorator to all the unit tests that we currently EXPECT to fail.
That way, the Travis-CI build test will pass - the failing tests will
just be skipped if they fail (still with an error message).

We shouldn't forget to go and fix the tests though!