MB-7483: Use ep_max_size not ep_max_data_size

We are removing the ep_max_data_size stat since it is a duplicate

Change-Id: If4393954df910072d79a3ccd3b8d735bd3b0d210
Reviewed-on: http://review.couchbase.org/26946
Tested-by: Michael Wiederhold <mike@couchbase.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>