Don't create a failover entry after a clean shutdown

We are only required to create new failover entries after a crash
so we should check to see if that happened before creating one
during warmup.

Change-Id: I128eceaca719f6e44e683e17223445a8b328cad5
Reviewed-on: http://review.couchbase.org/32895
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>