For a second we thought this was allocating but we were looking
at a CPU profile (which showed calls to mallocgc view makeslice)
instead of the alloc profile.
Updates golang/go#65685 (which if fixed wouldn't have confused us)
Change-Id: Ic0132310d52d8a65758a516142525339aa23b1ed
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>