mds: sync->mix replica state is sync->mix(2)
mds: sync->mix replica state is sync->mix(2)

When auth first moves to sync->mix,
 - auth sends AC_MIX to replicas
 - replicas go to sync->mix
 - replicas finish gather, send AC_SYNCACK, move to sync->mix(2)
 - auth gets all acks, sends AC_MIX again
 - replica moves to MIX

So any new replica should just get sync->mix(2), so that it is not confused
by the second AC_MIX.

Signed-off-by: Sage Weil <6dd34506bbd5e58221bbb3e4732d97c91f02277b@newdream.net>

ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph