fix underlay subnet kubectl ko trace error

[changluyi]

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

What type of this PR

Examples of user facing changes:

• Features
• Bug fixes
• Docs
• Tests

Which issue(s) this PR fixes:

Fixes #(issue-number)

WHAT

copilot:summary

copilot:poem

HOW

copilot:walkthrough

[github-actions]

• Priority 1: Line 283 has a syntax error where the variable "dstMac" is not enclosed in quotes. This could cause unexpected behavior and should be fixed.
• Priority 2: The function "ipIsInCidr" used on line 282 is not defined in this file, which could cause issues if it is not defined elsewhere. It would be better to define it within this file or ensure that it is imported from another file.
• Priority 3: The conditional statement on line 281 could be simplified by using the "-o" operator instead of nested if statements. This would make the code more concise and easier to read.
• Priority 4: The function "trace" does not have any input validation, which could lead to unexpected behavior if invalid arguments are passed in. It would be better to add input validation to ensure that the function is being used correctly.
• Priority 5: There are no comments explaining what the "trace" function does or how it is used. Adding comments would make the code easier to understand for future developers.