[bugfix] When add_eip, send a GARP for eip from net1

[kldancer]

[bugfix] When add_eip, send an ARP packet from net1 to the gateway to announce the EIP to the switch.

Pull Request

• Make sure you have followed Kube-OVN Code Style.

What type of this PR

Examples of user facing changes:

• Bug fixes

Which issue(s) this PR fixes

1. Restarting nat-gw will cause external access to EIP traffic to be interrupted and will not be automatically restored.
2. Therefore, when adding add_eip in the nat-gw script, actively send an arp request with src_ip as EIP and sent to the gateway to update the underlying switch arp information.
3. [BUG] 自定义VPC的Nat-gw pod重启，导致已存在的外部访问EIP的流量断开，且无法自动恢复。 #4690

[kldancer]

@bobz965 你好👋，有两个自动检查失败了，能帮我看一下是什么原因吗？

[bobz965]

@bobz965 你好👋，有两个自动检查失败了，能帮我看一下是什么原因吗？

不影响

[hackerain]

arping -D的意思是要去检查是否有IP冲突，把这个去掉不太好吧？

[bobz965]

arping -D的意思是要去检查是否有IP冲突，把这个去掉不太好吧？

看起来没有去掉，新增了一行

[hackerain]

哦哦，sorry，我看错了