identify 'this' node in terse bucket infos

It is done by thisNode attribute that's set to true for nodesExt entry
that represents node that is serving terse bucket info.

Change-Id: Ic75a37bf3d3f86d32cb5e7b92a2a95bccfec376d
Reviewed-on: http://review.couchbase.org/43569
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>