Double-check traffic stats when zero

On some old devices(like my poor MI-ONE Plus), the traffic stats used to stick on 0B/s forever. This patch does a workaround to the bug by checking traffic stats from /proc/net/dev when the original interface returns zero.

P.S. Forgive my commits from AIDE, you can only cherry-pick my latest commit. Do not merge my former commits. They are only for AIDE.