dm raid: streamline rs_get_progress() and its raid_status() caller side

Pass already deciphered state into rs_get_progress, simplify recovery offset
definition and combine two st_resync, st_reshape conditionals into one as is
already the case with st_check and st_repair.

Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>