improved ns-server-hierarchy.txt coverage of xdcr processes

Change-Id: I6ef7995e21515191f4e3693e930e7697e8937099
Reviewed-on: http://review.couchbase.org/42434
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>