cros_vm_lib: Port forward to VM only from localhost.

Stop forwarding traffic from any address for the host machine.

BUG=chromium:496756
TEST=Trybot with VMTest succeeds.

Change-Id: I8bdce2976003e23c97ecb8a2549ecfe2fe45386e
Reviewed-on: https://chromium-review.googlesource.com/275300
Reviewed-by: mukesh agrawal <quiche@chromium.org>
Commit-Queue: Prathmesh Prabhu <pprabhu@chromium.org>
Tested-by: Prathmesh Prabhu <pprabhu@chromium.org>
1 file changed