Don't save reporting district to RawResult.district

In Maryland, results are available at the state legislative
district reporting level.

The district from this reporting level was getting parsed out
of a value that would become the ``jurisdiction`` field and
assigned as the ``district`` field.  So, records for presidential
results or U.S. House results were getting a state legislative
district overwriting the correct district parsed elsewhere in
the loader.

This incorrect district prevented correctly looking up canonical
``Office`` records in a transform step.

Addresses #49