Fix: one NIC's IP pool shortage depleted IPs of other NICs in a multi-NIC setup.

[ty-dc]

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What issue(s) does this PR fix:

Fixes #4295

Special notes for your reviewer:

问题现象：
在 pod 使用 多 underlay 网卡时，若第一张网卡分配 IP 成功，第二张网卡因为ip不足而分配失败，会导致 pod 重启，而在重启后，第一张网卡会再次分配新的 ip .... 如此往复，会导致第一张网卡的 ip 池 ip 耗尽，同一个 Pod 的 UID 在池中被重复记录，导致该池资源被耗尽，无法为其他 Pod 提供地址分配。

kubectl get sp default-v4-ippool -ojsonpath={.status.allocatedIPs} | jq 
{
  "172.18.40.10": {
    "pod": "default/ippool-test-app-58b7766c7c-mvwpf",
    "podUid": "4009cb83-bd17-4b08-92f0-2ea0cd3d64fc"
  },
  "172.18.40.11": {
    "pod": "default/ippool-test-app-58b7766c7c-5jp5d",
    "podUid": "4e57d4ee-fd3f-44fa-8c80-1db2c6ae0e98"
  },
  "172.18.40.12": {
    "pod": "default/ippool-test-app-58b7766c7c-gw8hd",
    "podUid": "4102bd95-8f63-4f66-9b64-d7050e91b6c5"
  },
  "172.18.40.13": {
    "pod": "default/ippool-test-app-58b7766c7c-gw8hd",
    "podUid": "4102bd95-8f63-4f66-9b64-d7050e91b6c5"
  },
  "172.18.40.19": {
    "pod": "default/ippool-test-app-58b7766c7c-gw8hd",
    "podUid": "4102bd95-8f63-4f66-9b64-d7050e91b6c5"
  },
  "172.18.40.20": {
    "pod": "default/ippool-test-app-58b7766c7c-gw8hd",
    "podUid": "4102bd95-8f63-4f66-9b64-d7050e91b6c5"
  }
}

原因：
在多网卡场景下，根据网卡依次调用 IPAM 为每张网卡进行地址分配。如 Pod 拥有网卡 eth0、net1。当 Pod 启动，先为 eth0 进行 IP 地址分配，然后为 net1 网卡进行地址分配。如果此时 net1 所使用的 IP 池地址资源不够，将分配 IP 地址失败，然后 IPAM 会进行循环重试分配，又会从 eth0 开始进行分配，故同一个 Pod 的 eth0 网卡会被 IP 池多次分配。直到 IP 池地址耗尽。

解决：

检查 IP 池中已分配的 IP 情况，如果对应的 UID 和当前需要分配的 Pod 的 UID 匹配，证明 Pod 的某张卡已经在该池中拿到了 IP 地址，无需继续分配，返回当前拥有的 IP 地址，以此避免重复分配导致 IP 地址被耗尽的问题。

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.85%. Comparing base (e3b8408) to head (834562d).
Report is 34 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4379      +/-   ##
==========================================
+ Coverage   79.56%   79.85%   +0.28%     
==========================================
  Files          54       54              
  Lines        6362     6369       +7     
==========================================
+ Hits         5062     5086      +24     
+ Misses       1103     1082      -21     
- Partials      197      201       +4     

Flag	Coverage Δ
unittests	79.85% <100.00%> (+0.28%)	⬆️

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

Files with missing lines	Coverage Δ
pkg/ippoolmanager/ippool_manager.go	84.61% <100.00%> (-2.03%)	⬇️

... and 1 file with indirect coverage changes

[cyclinder]

感觉 info 级别就可以