MB-11546: Check node status before failover

If node status is not healthy, automatically use hard failover.

Change-Id: I374f7af250b9bb3775ec71208957643a95d268ad
Reviewed-on: http://review.couchbase.org/38902
Tested-by: Bin Cui <bin.cui@gmail.com>
Reviewed-by: Bin Cui <bin.cui@gmail.com>