service.Run: replace signal SIGKILL with SIGQUIT

According to "os/signal" documentation [1] and libc manual [2], SIGKILL
may not be caught by a program.

[1] https://godoc.org/os/signal
[2] https://www.gnu.org/software/libc/manual/html_node/Termination-Signals.html

service.go

@@ -153,7 +153,7 @@ func (s *service) Run() error {
 	go s.run(ex)
 
 	ch := make(chan os.Signal, 1)
-	signal.Notify(ch, syscall.SIGTERM, syscall.SIGINT, syscall.SIGKILL)
+	signal.Notify(ch, syscall.SIGTERM, syscall.SIGINT, syscall.SIGQUIT)
 
 	select {
 	// wait on kill signal