fix(dnstap source): close TCP connection after sending FINISH to prevent CLOSE_WAIT socket leak

[jpds]

Summary

After sending a FrameStream FINISH frame in response to a client STOP, explicitly shut down the write side of the TCP connection. Per the FrameStream protocol, the server should initiate TCP close after FINISH. Without this, sockets accumulate in CLOSE_WAIT indefinitely because the client may wait for the server to close first, creating a protocol-level deadlock.

Vector configuration

How did you test this PR?

Simple change to TCP behaviour.

Change Type

• Bug fix
• New feature
• Dependencies
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the no-changelog label to this PR.

References

Fixes #24838

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[jpds]

@esensar Please review when you have a moment.