Ever since version v6.5.0 of iproute2, iproute2 no longer automatically
creates the /etc/iproute2 files, instead preferring to add files to
/usr/lib/iproute2 and then later on /usr/share/iproute2.
This adds fallback path matching to kube-router so that it can find
/etc/iproute2/rt_tables wherever it is defined instead of just failing.
This also means people running kube-router in containers will need to
change their mounts depending on where this file is located on their
host OS. However, ensuring that this file is copied to `/etc/iproute2`
is a legitimate way to ensure that this is consistent across a fleet of
multiple OS versions.
