v1.18.4: cpuCFSQuotaPeriod

• Kubernetes: 1.18.4
• Kubelet config: set default cpuCFSQuotaPeriod to 10ms. See kubernetes#67577 for details
• Security: Bump rack from 2.1.2 to 2.2.3
• Kubernetes: addon_manager v9.1.1
• Node Problem Detector: 0.8.2
• Weave Net: 2.6.5
• CoreDNS: 1.7.0