Revert "MB-11917: Bump reductions before the NIF call"

It lead to utilisation of a single core only.

This reverts commit 4b467172df476b42c8acca985492bb0abc484d83.

Change-Id: I024d9006127318c0dd8153b4aeda1e06220b5a26
Reviewed-on: http://review.couchbase.org/40616
Reviewed-by: Volker Mische <volker.mische@gmail.com>
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Sarath Lakshman <sarath@couchbase.com>