Since we determine the connectivity state of each device individually,
the global connectivity state is an aggregate of all these states.

I am not sure about considering here devices that don't have the (best)
default route for their respective address family. But anyway.

When we aggregate the best connectivity, we chose the numerical largest
value. That is wrong, because PORTAL is numerically smaller than
LIMITED.

That means, if you have two devices, one with connectivity LIMITED and
one with connectivity PORTAL, then LIMITED wrongly wins.

Fixes: 6b7e9f9b

https://bugzilla.redhat.com/show_bug.cgi?id=1619873