MB-9957: Update according to transport spec change

The NRU field was added to the mutation response.

Change-Id: I0c1d2c67d1a8d03ec3609e742ad6b15eb718f411
Reviewed-on: http://review.couchbase.org/32869
Reviewed-by: Sarath Lakshman <sarath@couchbase.com>
Reviewed-by: Pratap Chakravarthy <prataprc@gmail.com>
Reviewed-by: Volker Mische <volker.mische@gmail.com>
Tested-by: buildbot <build@couchbase.com>