Fix Windows support for 2019 (#47)

Switching Windows container image to
mcr.microsoft.com/oss/kubernetes/windows-host-process-containers-base-image:v1.0.0
so that all Windows container versions are supported.

kubectl-node_shell

@@ -97,12 +97,10 @@ os="$($kubectl get node $node -o jsonpath="{.metadata.labels.kubernetes\.io/os}"
 
 # Set pod configuration per operating system
 if [ "$os" = "windows" ]; then
-  image="${KUBECTL_NODE_SHELL_IMAGE_WINDOWS:-mcr.microsoft.com/powershell}"
+  image="${KUBECTL_NODE_SHELL_IMAGE_WINDOWS:-mcr.microsoft.com/oss/kubernetes/windows-host-process-containers-base-image:v1.0.0}"
   name="pwsh"
   pod="${name}-$(env LC_ALL=C tr -dc a-z0-9 </dev/urandom | head -c 6)"
-  # pwsh has to be launched via cmd.exe because of how containerd 1.6 handles the mount of the container filesystem
-  # see https://kubernetes.io/docs/tasks/configure-pod-container/create-hostprocess-pod/#volume-mounts
-  cmd_start='"cmd.exe", "/c", "%CONTAINER_SANDBOX_MOUNT_POINT%\\Program Files\\PowerShell\\latest\\pwsh.exe", "-nol", "-wd", "C:\\"'
+  cmd_start='"cmd.exe", "/c", "powershell.exe", "-nol"'
   cmd_arg_prefix=', "-Command"'
   cmd_default=''
   security_context='{"privileged":true,"windowsOptions":{"hostProcess":true,"runAsUserName":"NT AUTHORITY\\SYSTEM"}}'