Do not fire ContainerMemoryUsage alert for unlabelled metrics
The prometheus query we use for ContainerMemoryUsage
alert
(sum(container_memory_working_set_bytes) BY (container) / sum(container_spec_memory_limit_bytes > 0) BY (container) * 100) > 80
regularly leads to alerts that do not have the container
label set. It seems that those metrics are redundant and/or aggregate versions of the ones that do have the container
label. Therefore we should adapt the query to leave out those unlabelled metrics.