IPv4 connectivity does not work as expected with NetworkManager 1.12.0 in RHEL 7.6 because the "prefix" route is missing

Issue

• With NetworkManager 1.12.0, sometimes a connection is marked active and the IPv4 address is assigned but basic IP connectivity does not work. Closer inspection shows the system's routing table does not include the expected "prefix" (aka directly connected or "onlink") route.

• May affect MACSEC interfaces.