nixos/test/networking: test bonding netdev creation
nixos/test/networking: test bonding netdev creation

Previously the bonding driver would create an initial `bond0` interface
when it was loaded. If the network management integration used that
interface and did not recreate it, it was stuck to the default
`balance-rr` mode.

Deploying systemds modprobe.d configuration sets `max_bonds=0`, so we
don't run into that issue anymore.

Hence we now make sure that we can indeed create `bond0` with `802.3ad`
(LACP), which is a non default mode.

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