Useless code path in import_from_xml causing errors removed

@dianakhuang @sarina @nasthagiri 

It appears as if a useless code path was causing @carsongee errors while importing course from command line.

@carsongee Can you verify that this fixes your issue?
Please update the docstring to the following:

If True, then a new course is created if it doesn't already exist.  The check for existing courses is case-insensitive.