Update offline tools script

Created by: pixiake

Update Default Version:

KubernetesVersionDefault: v1.17.9 -> v1.21.5
HELM_VERSION: v3.2.1 -> v3.6.3
CNI_VERSION: v0.8.6 -> v0.9.1

Add etcd binary:

ETCD_VERSION: v3.4.13

Signed-off-by: pixiake guofeng@yunify.com