Nowadays network interfaces have names like docker0, team0, ip_vti0, eno,
wlp61s0 and so on. Including word "Interface" in beginning of
graph_title groups these graphs together in web interface, not randomly
before/after other network-graphs (ipconntrack, firewall, ...).
See commit 70711831c44 in munin repository for similar change.
e6f5722a04