MB-5307 Don't do unneeded list copies.

Change-Id: I2315e8ed62cabc2d86fb4e8a71843817c4b7a3b9
Reviewed-on: http://review.couchbase.org/25298
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>