The numbers will only be available when docker.service has its own
memory and cpu cgroups, which doesn't necessarily happen unless the unit
has Delegate=yes configured.

Let's work around that by checking the status of Delegate, in the case
where we are:
* running Docker
* running Systemd
* able to check the status through systemctl
* the status is explicitly Delegate=no (the default)

If all of those are true, let's make CPU and Memory expectations
optional.

Tested: make test-e2e-node REMOTE=true HOSTS=centos-e2e-node FOCUS="Summary API"