postgres_fdw: make_tuple_from_result_row should set cur_attno for ctid.

postgres_fdw: make_tuple_from_result_row should set cur_attno for ctid.

There's no reason for this function to do this for every other
attribute number and omit it for CTID, especially since
conversion_error_callback has code to handle that case.  This seems
to be an oversight in commit e690b9515072fd7767fdeca5c54166f6a77733bc.

Etsuro Fujita