md: don't update curr_resync_completed without also updating reshape_position.

md: don't update curr_resync_completed without also updating reshape_position.

In order for the metadata to always be consistent, we mustn't updated
curr_resync_completed without also updating reshape_position.

The reshape code updates both at the same time.  However since
commit c466ab793490242a4dbe8d8b5b5c54a33e3cb3d7
the common md_do_sync will sometimes update curr_resync_completed
but is not in a position to update reshape_position.
So if MD_RECOVERY_RESHAPE is set (indicating that a reshape is
happening, so reshape_position might change), don't update
curr_resync_completed in md_do_sync, leave it to the per-personality
reshape code.

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