rename Metadata Ejection to Cache Metadata in bucket details

Change-Id: I97d6171fbb6a8833173ae823376f5bb5eee8b340
Reviewed-on: http://review.couchbase.org/40374
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>