runtime: fix overflow in PingPongHog test

runtime: fix overflow in PingPongHog test

On 32-bit systems the result of hogCount*factor can overflow.
Use division instead to do comparison.

Update #52207

Change-Id: I429fb9dc009af645acb535cee5c70887527ba207
Reviewed-on: https://go-review.googlesource.com/c/go/+/407415
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Keith Randall <khr@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@google.com>