Run curl with sudo in kubectl-checkpoint

Previously, the curl command could not access
the kubelet's client certificate and key.

examples/container_migration_in_kubernetes/kubectl-plugin/kubectl-checkpoint

@@ -13,7 +13,7 @@ elif [ "$#" -ne 3 ]; then
 	exit 1
 fi
 
-curl --insecure \
+sudo curl --insecure \
 	--cert /var/lib/kubelet/pki/kubelet-client-current.pem \
 	--key /var/lib/kubelet/pki/kubelet-client-current.pem \
 	-X POST \