If the host is running with cgroup-v2, RSS and Max Usage doesn't get
reported anymore.

If the docker engine is running on cgroup-v2 host, then RSS and Max
Usage doesn't get reported.

Using a heauristic here to avoid adding more API calls to the Docker
Engine to infer cgroups version. Also, opted to avoid coordinating stats
collection with fingerprinting, which adds concurrency complexities.

If a task doesn't report RSS, let's use memory usage.