wait until the network is back up after running 'netplan apply'

[honzatlusty]

After running 'netplan apply', it takes a short while before the network is usable again.

root@ubuntu:~# netplan apply && for i in $(seq 1 10); do systemctl status systemd-networkd &> /dev/null; echo $?; done
3
3
3
3
3
3
0
0
0

If puppet attempts to use the network during this time (install packages), it results in a failed puppet run. One way to deal with this is to set ordering rules for all the resources outside of this module that could be affected. But I think it makes sense to assume the network is in the desired state when when puppet finishes applying the netplan class.