cni-server: do not perform ipv4 conflict detection during VM live migration

[zhangzujian]

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What type of this PR

• Bug fixes

Which issue(s) this PR fixes:

Fixes #2659

WHAT

🤖 Generated by Copilot at 02988f1

Improve pod migration and IP conflict detection in VLAN subnets. The change modifies handler.go to skip unnecessary ping checks and remove a redundant variable assignment.

🤖 Generated by Copilot at 02988f1

To move pods in VLANs without stress
We added detectIPConflict yes
We skip the ping check
To avoid a wreck
And removed a redundant excess

HOW

🤖 Generated by Copilot at 02988f1

• Add a variable detectIPConflict to control IP conflict detection for pods in VLAN subnets (link)
• Skip ping checks to the gateway for migrating pods in VLAN subnets (link, link)
• Remove redundant assignment of detectIPConflict to true (link)

[github-actions]

• The commit message is missing. It should provide a clear and concise description of the changes made in this patch.
• There is a potential bug in the code. The detectIPConflict variable is being set to false unconditionally, which may cause IP conflicts to go undetected.
• There is a format error in the code. The line detectIPConflict := podSubnet.Spec.Vlan != "" is repeated twice, once before the conditional statement and once inside it. This repetition should be removed.
• There are no obvious performance issues in the code.
• One way to improve the code would be to refactor the conditional statement that sets detectIPConflict to make it clearer and easier to understand.

[github-actions]

• The commit message is missing. It should provide a clear and concise description of the changes made in this patch.
• There is a potential bug in the code. The detectIPConflict variable is initialized to podSubnet.Spec.Vlan != "" before the if statement that checks for live migration. If the pod is being live migrated, the value of detectIPConflict will not be updated and may cause conflicts with other IP addresses.
• There is a format error in the code. Line 271 has an extra space after the comma in the log message.
• There is a performance issue in the code. The routes slice is being appended to itself, which can be slow for large slices. Consider using a separate slice to avoid this issue.
• There is a way to improve the code. The if statement on line 241 can be simplified by combining the conditions with an && operator.