CCBC-352: never return nmv origin index

Change-Id: I7197e3778cdbe7f77062da4fcd0bccd655d1f9ec
Reviewed-on: http://review.couchbase.org/34899
Reviewed-by: Subhashni Balakrishnan <b.subhashni@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>