Pick the right Network interface
Pick the right Network interface

On Docker / macOS, there is a tun10 and a eth0, so we pick the right one
to check for traffic to avoid flakes

Signed-off-by: Davanum Srinivas <36003aec7ba325a16727bc9a176c12d2776a8ce4@gmail.com>

linux-on-ibm-z/cadvisor,linux-on-ibm-z/cadvisor,linux-on-ibm-z/cadvisor