fix: leak flag in client and server package

[knakul853]

closes: https://github.com/projectdiscovery/interactsh/issues/1245 in nuclei tests during parallel execution we had observed server and client package getting flagged as goroutine leaks. it was reproducible from the issue https://github.com/projectdiscovery/interactsh/issues/1245 added cleanup and avoid starting goroutine when client is created(it starts now when needed) and in server added cleanup state.

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✨ Finishing touches

🧪 Generate unit tests

• [ ] Create PR with unit tests
• [ ] Post copyable unit tests in a comment
• [ ] Commit unit tests in branch fix/goleak-client-server

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[knakul853]

relates: https://github.com/projectdiscovery/nuclei/pull/6490