packer/plugin: swallowInterrupts in plugin should swallow all

packer/plugin/plugin.go

@@ -94,8 +94,10 @@ func swallowInterrupts() {
 	signal.Notify(ch, os.Interrupt)
 
 	go func() {
+		for {
 			<-ch
 			log.Println("Received interrupt signal. Ignoring.")
+		}
 	}()
 }