mds: use direct replay test when deciding whether to rebalance.
mds: use direct replay test when deciding whether to rebalance.

The previous use of standby_for_rank testing was prone to errors
and I think would have ended up causing bugs if it was in the middle
of a standby_replay run when it got a new MDS map pushing
it into regular replay mode.

Signed-off-by: Greg Farnum <7c97bbd3e62ab6303ee1daebcbc2d9d58823df1a@hq.newdream.net>

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