Clean up redundant DNS related kubelet codes

Signed-off-by: Zihong Zheng <zihongz@google.com>

pkg/kubelet/container/runtime.go

@@ -428,10 +428,6 @@ type RunContainerOptions struct {
 	// this directory will be used to create and mount the log file to
 	// container.TerminationMessagePath
 	PodContainerDir string
-	// The list of DNS servers for the container to use.
-	DNS []string
-	// The list of DNS search domains.
-	DNSSearch []string
 	// The parent cgroup to pass to Docker
 	CgroupParent string
 	// The type of container rootfs