CBD-931: add read-only config with reduced throughput

Change-Id: Ia9cc0b715e669c756328b829adea5aa1b8ffbd84
Reviewed-on: http://review.couchbase.org/25573
Reviewed-by: Pavel Paulau <pavel.paulau@gmail.com>
Tested-by: Pavel Paulau <pavel.paulau@gmail.com>