Defaults: replace docker with containerd as our default container_manager (#8175)

* Defaults: replace docker with containerd as our default container_manager

* CI: Use docker for download_localhost test

* Defaults: with container_manager=containerd we need etcd_deployment_type=host

* CI: Run weave jobs with docker

* CI: Vagrant don't download_force_cache

* CI: Fix upgrade tests

* should run compatible with old settings, this means docker
* we need to run with a distro that has at least modern containerd,
  this means move from debian9 to debian10 to allow `containerd_version`
  to match between 2.17 and master

tests/files/packet_ubuntu20-docker.yml

@@ -0,0 +1,19 @@
+---
+# Instance settings
+cloud_image: ubuntu-2004
+mode: aio
+vm_memory: 1600Mi
+
+# Kubespray settings
+deploy_netchecker: true
+dns_min_replicas: 1
+
+# Currently ipvs not available on KVM: https://packages.ubuntu.com/search?suite=focal&arch=amd64&mode=exactfilename&searchon=contents&keywords=ip_vs_sh.ko
+kube_proxy_mode: iptables
+enable_nodelocaldns: False
+
+auto_renew_certificates: true
+
+# Use docker
+container_manager: docker
+etcd_deployment_type: docker