Serve stored a Background context for tailsql and called
context.Done() during signal shutdown. Done only returns the
done channel and does not cancel, so tailsql never stopped
when Headscale shut down.
Create a cancellable child of the Serve context, run
`runTailSQLService` in the listener errgroup so its error is
surfaced, and call the cancel func on shutdown - tailsql
unblocks on ctx.Done.
(cherry picked from commit a9f80d8802)
Igor Serganov
032470a5d3