DDF: Don't fail compare_super_ddf due to re-configure changes.

DDF: Don't fail compare_super_ddf due to re-configure changes.

It is possible that one device has seem some reconfig but the other
hasn't.  In that case  they are still the "same" DDF, even though
one might be older.  Such age will be detected by 'seq' differences.

If A is new and B is old, then it is import that
  mdadm -I B
  mdadm -I A

doesn't get confused because A has the same uuid as B, but compare_super fails.

So: if the seq numbers are different, then just accept as two
different superblocks.
If they are the same, then look to copy data from new to old.

Signed-off-by: NeilBrown <neilb@suse.de>