Comment 6 for bug 1709135

Installed nplan 0.29 from artful to get it process the test-case yaml, to then test networkd portion is working right.

Using:
# cat /etc/netplan/bond-primary.yaml
network:
  version: 2
  ethernets:
    eth0:
      match:
        name: eth0
    dummy0:
      match:
        driver: dummy
  bonds:
    bond0:
      interfaces: [eth0, dummy0]
      parameters:
        mode: active-backup
        mii-monitor-interval: 100
        primary: eth0
      dhcp4: true

229-4ubuntu19
Oct 02 15:37:21 test-upgrade systemd-networkd[1773]: [/run/systemd/network/10-netplan-eth0.network:8] Unknown lvalue 'PrimarySlave' in section 'Network'
Oct 02 15:37:21 test-upgrade systemd-networkd[1773]: bond0: IPv6 enabled for interface: Success

229-4ubuntu20
Oct 02 15:39:22 test-upgrade systemd[1]: Starting Network Service...
Oct 02 15:39:22 test-upgrade systemd-networkd[3821]: bond0: IPv6 enabled for interface: Success
Oct 02 15:39:22 test-upgrade systemd-networkd[3821]: bond0: netdev ready
Oct 02 15:39:22 test-upgrade systemd-networkd[3821]: eth0: Gained IPv6LL
Oct 02 15:39:22 test-upgrade systemd-networkd[3821]: Enumeration completed
Oct 02 15:39:22 test-upgrade systemd[1]: Started Network Service.

All is good.