[BLOCK] Add hints & FAQ for network blocker: more than one ethnic* interface

[atoomic]

Using more than a single interface like eth0, eth1, ... is a common pattern we could expect from more than one customer

We should consider:

1. Provide a more friendly error message and provide some hints on how to rename and what are the good practice to rename a NIC
2. Add one FAQ entry for Renaming eth1

        Your machine has multiple network interface cards (NICs) using kernel-names (ethX).
        Since the upgrade process cannot guarantee their stability after upgrade, you cannot upgrade.

        Please provide those interfaces new names before continuing the update.

but what's next?

Some naming convention: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/networking_guide/ch-consistent_network_device_naming

en → Ethernet
ib → InfiniBand
sl → Serial line IP (SLIP)
wl → WLAN
ww → WWAN

How to rename a NIC: https://www.baeldung.com/linux/rename-network-interface

[toddr]

RE-276