Refer to record fields uniformly in auto_failover_logic.

Change-Id: I0fba8b96fb77cc812a4701cbd06121d2115736b5
Reviewed-on: http://review.couchbase.org/32620
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>