[IPAM] fix liqoctl builds by avoiding importing nftables

[fra98]

Description

This PR fixes the liqoctl build on arch different from Linux, by avoiding importing the nftables library (known to be compatible only on Linux). In particular, the NetFirstAndLastIP() function is copied from the library into the Liqo source code (avoiding importing the library).

[adamjensenbot]

Hi @fra98. Thanks for your PR!

I am @adamjensenbot.
You can interact with me issuing a slash command in the first line of a comment.
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• /rebase: Rebase this PR onto the master branch (You can add the option test=true to launch the tests
  when the rebase operation is completed)
• /merge: Merge this PR into the master branch
• /build Build Liqo components
• /test Launch the E2E and Unit tests
• /hold, /unhold Add/remove the hold label to prevent merging with /merge

Make sure this PR appears in the liqo changelog, adding one of the following labels:

• kind/breaking: 💥 Breaking Change
• kind/feature: 🚀 New Feature
• kind/bug: 🐛 Bug Fix
• kind/cleanup: 🧹 Code Refactoring
• kind/docs: 📝 Documentation

[fra98]

/build