env/openbsd-amd64: fix network configuration for GCE

The network configuration specified by the GCE DHCP server does not
work correctly on OpenBSD 6.0. Add a hack that reconfigures the
network using a 10.0.0.0/8 network with a high priority route.

Updates golang/go#16951

Change-Id: I8100f34ac48411c885478e72c083754e57c14aa7
Reviewed-on: https://go-review.googlesource.com/34172
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
1 file changed