Windows: Fixes /etc/hosts file mounting support for containerd

If Containerd is used on Windows, then we can also mount individual
files into containers (e.g.: /etc/hosts), which was not possible with Docker.

Checks if the container runtime is containerd, and if it is, then also
mount /etc/hosts file (to C:\Windows\System32\drivers\etc\hosts).

pkg/kubelet/kubelet.go

@@ -144,7 +144,8 @@ const (
 	evictionMonitoringPeriod = time.Second * 10
 
 	// The path in containers' filesystems where the hosts file is mounted.
-	etcHostsPath = "/etc/hosts"
+	linuxEtcHostsPath   = "/etc/hosts"
+	windowsEtcHostsPath = "C:\\Windows\\System32\\drivers\\etc\\hosts"
 
 	// Capacity of the channel for receiving pod lifecycle events. This number
 	// is a bit arbitrary and may be adjusted in the future.
@@ -177,6 +178,15 @@ const (
 	nodeLeaseRenewIntervalFraction = 0.25
 )
 
+var etcHostsPath = getContainerEtcHostsPath()
+
+func getContainerEtcHostsPath() string {
+	if sysruntime.GOOS == "windows" {
+		return windowsEtcHostsPath
+	}
+	return linuxEtcHostsPath
+}
+
 // SyncHandler is an interface implemented by Kubelet, for testability
 type SyncHandler interface {
 	HandlePodAdditions(pods []*v1.Pod)