runtime/race: fix finalizer tests After "runtime: combine small NoScan allocations" finalizers for small objects run more non deterministically. TestRaceFin episodically fails on my darwin/amd64.
runtime/race: fix finalizer tests
After "runtime: combine small NoScan allocations" finalizers
for small objects run more non deterministically.
TestRaceFin episodically fails on my darwin/amd64.

LGTM=khr
R=golang-codereviews, khr, dave
CC=golang-codereviews
https://codereview.appspot.com/56970043

firebitsbr/golang-old,wesolows/golang-old,wesolows/golang,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang-old,wesolows/golang-old,wesolows/golang-old,wesolows/golang,wesolows/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang,firebitsbr/golang-old,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang,wesolows/golang,wesolows/golang,firebitsbr/golang-old,wesolows/golang,firebitsbr/golang-old