xfs_repair: don't clear . or .. in process_dir2_data

xfs_repair: don't clear . or .. in process_dir2_data

process_dir2_data() has special . and .. processing; it is able
to correct these inodes, so there is no reason to clear them.

Do this before we adjust a length 0 filename to length 1, so
that we don't take this action on an accidentally created "."
name from a hidden dotfile.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>