MB-9343 introducing DEBUG_UPR macro that enables UPR replication

... for tap rebalanced buckets

to enable add {d, 'DEBUG_UPR', true} to rebar.config and rebuild ns_server

Change-Id: I3e7011c3ed7b9bcb0b554bc45326c7a417b26313
Reviewed-on: http://review.couchbase.org/32583
Tested-by: Artem Stemkovski <artem@couchbase.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>