MB-11433 use correct prefix for view related stats

Change-Id: If46173c0ed7f0d184cb4c401d52fc4a162f4f72c
Reviewed-on: http://review.couchbase.org/38842
Tested-by: Artem Stemkovski <artem@couchbase.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>