internal/netlink: wrap netpoll via context

This removes netpoll boilerplate for the most common use case.

Signed-off-by: Ophestra <cat@gensokyo.uk>

container/init.go

@@ -7,6 +7,7 @@ import (
 	"log"
 	"os"
 	"os/exec"
+	"os/signal"
 	"path"
 	"slices"
 	"strconv"
@@ -175,7 +176,11 @@ func initEntrypoint(k syscallDispatcher, msg message.Msg) {
 	}
 
 	if !params.HostNet {
-		k.mustLoopback(msg)
+		ctx, cancel := signal.NotifyContext(context.Background(), CancelSignal,
+			os.Interrupt, SIGTERM, SIGQUIT)
+		defer cancel() // for panics
+		k.mustLoopback(ctx, msg)
+		cancel()
 	}
 
 	// write uid/gid map here so parent does not need to set dumpable