Comment 7 for bug 1774666

Looking at the MAAS curtin configuration, I see the following:

  - bond_interfaces:
    - enp5s0f0
    - enp5s0f1
    - enp6s0f0
    - enp6s0f1
    id: eth1
    mac_address: 00:1b:21:4a:99:50
    mtu: 9000
    name: eth1
    params:
      bond-downdelay: 0
      bond-lacp-rate: fast
      bond-miimon: 100
      bond-mode: 802.3ad
      bond-updelay: 0
      bond-xmit-hash-policy: encap3+4
    subnets:
    - type: manual
    type: bond

The resulting netplan configuration, however, doesn't include an MTU. On the other hand, the Xenial configuration does correctly have the MTU for the bond.

As such, this seems like an issue in cloud-init to me.