libovsdb: fix potential duplicate addresses

[zhangzujian]

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

What type of this PR

• Bug fixes

Which issue(s) this PR fixes:

Fixes #(issue-number)

WHAT

🤖 Generated by Copilot at c5dc560

Optimize address set operations in ovn-nb-address_set.go. Avoid redundant deduplication in update function and move it to create function.

🤖 Generated by Copilot at c5dc560

To optimize address set ops
We tweaked some functions and props
We removed dedupe
From AddressSetUpdate
And added it to AddressSetAdd tops

HOW

🤖 Generated by Copilot at c5dc560

• Remove unnecessary deduplication of addresses slice in AddressSetUpdateAddress function (link)
• Add deduplication of addresses slice in AddressSetAddAddress function to prevent errors and inconsistencies (link)

[github-actions]

• The code changes in ovn-nb-address_set.go may cause a bug. The util.UniqString() function is called after formatting the CIDR, which means that if there are duplicate elements in the slice before formatting, they will not be removed. This can cause an error when updating the address set. It would be better to call util.UniqString() before formatting the CIDR.