Ensure kernel sends GARPs to avoid communication failures

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What issue(s) does this PR fix:

Fixes #4650

Special notes for your reviewer:

正常情况下，IPAM 分配 IP 给 CNI， CNI 将 IP 地址配置到网卡之后，最后设置状态为 UP。当网卡的链路地址改变或状态改变时，内核会发送免费 ARP，宣告其地址。

#4588 为了修复检测失败时因为错误的 ARP 缓存表导致通信失败，在 IPAM 执行冲突检测。这会提前将网卡 UP，执行完冲突检测之后，返回 IP 地址给 CNI，CNI 将地址配置到网卡，最 后UP 网卡的时候，网卡已经是 UP 的状态，所以这不会触发内核发送免费 ARP 通告其地址。这会导致当 Pod 以相同的 IP 重启后，与其通信过的其他主机不会主动更新 ARP 缓存表导致通信失败。

此 PR 通过在 IPAM 做完冲突检测之后，将网卡的状态设置为 Down，以便 CNI 可以在 UP 网卡时触发免费ARP。

Normally, IPAM assigns IP to the CNI, and the CNI configures the IP address to the NIC before finally setting the status to UP. the kernel sends a free ARP announcing the address of the NIC when its link address is changed or the status is changed.

#4588 To fix a detection failure when communication fails due to an incorrect ARP cache table, conflict detection is performed at IPAM. This will bring the card up early, and after conflict detection, it will return the IP address to the CNI, which will configure the address to the card, and when the card is finally brought up, it will already be up, so this will not trigger the kernel to send a free ARP announcing its address. This can lead to communication failures when the Pod reboots with the same IP and other hosts it has communicated with do not actively update the ARP cache table.

This PR is accomplished by setting the status of the NIC to Down after IPAM has done conflict detection so that the CNI can trigger the free ARP notification when the NIC is UP.

[codecov]

Codecov Report

Attention: Patch coverage is 60.00000% with 6 lines in your changes missing coverage. Please review.

Project coverage is 75.24%. Comparing base (62d4e07) to head (e128d86).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
cmd/spiderpool/cmd/command_add.go	60.00%	4 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4649      +/-   ##
==========================================
- Coverage   75.28%   75.24%   -0.05%     
==========================================
  Files          56       56              
  Lines        6765     6778      +13     
==========================================
+ Hits         5093     5100       +7     
- Misses       1462     1466       +4     
- Partials      210      212       +2     

Flag	Coverage Δ
unittests	75.24% <60.00%> (-0.05%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
cmd/spiderpool/cmd/command_add.go	68.25% <60.00%> (-1.07%)	⬇️