merge-recursive: Don't re-sort a list whose order we depend upon

merge-recursive: Don't re-sort a list whose order we depend upon

In record_df_conflict_files() we would resort the entries list using
df_name_compare to get a convenient ordering.  Unfortunately, this broke
assumptions of the get_renames() code (via string_list_lookup() calls)
which needed the list to be in the standard ordering.  When those lookups
would fail, duplicate stage_data entries could be inserted, causing the
process_renames and process_entry code to fail (in particular, a path that
that process_renames had marked as processed would still be processed
anyway in process_entry due to the duplicate entry).

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>