undo CL 8954044 / ad3c2ffb16d7

It works on i386, but fails on amd64 and arm.

??? original CL description
runtime: prevent the GC from seeing the content of a frame in runfinq()

Fixes issue 5348.

R=golang-dev, dvyukov
CC=golang-dev
https://codereview.appspot.com/8954044
???

R=golang-dev, r
CC=golang-dev
https://codereview.appspot.com/8695051