When creating AIP recovery location, don't hardcode space or relative_path

Otherwise, if the default AIP recovery location is changed, the
Storage Service will set up a second recovery location on startup.
This will subsequently cause errors in locations that try to use
Location.get() to fetch results, since there will be two.

Instead, get_or_create() should only consider the purpose when fetching
a result and supply a defaults dict to use only when creating a new
one.