Depending on whether the data source is registered, either
rDescriptor[svx::daDataSource]
or
rDescriptor[svx::daDatabaseLocation]
will be filled in (and should be used).

Luckily, ODataAccessDescriptor provides a utility
function that will automatically return the one
that is set. Use that instead of hardcoding svx::daDataSource.

Thank you Lionel!

Change-Id: I02673e7924c4323915dea579015326194c3f5077