ns_config:search/1 to do lookup in ns_config_ets_dup instead of

... ns_config:eval. because it is faster.

Change-Id: I8681a778b80ab92ded80fa0f35e04ad7b19cfe08
Reviewed-on: http://review.couchbase.org/37012
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>