BUG/MINOR: systemd: propagate the correct signal to haproxy

Some people report that sometimes there's a collection of old processes
after a restart of the systemd wrapper. It's not surprizing when reading
the code, the SIGTERM is propagated as a SIGINT which asks for a graceful
stop instead. If people ask for termination, we should terminate.

src/haproxy-systemd-wrapper.c

@@ -147,7 +147,7 @@ static void do_shutdown(int sig)
 		if (pid > 0) {
 			fprintf(stderr, SD_DEBUG "haproxy-systemd-wrapper: %s -> %d.\n",
 			        sig == SIGTERM ? "SIGTERM" : "SIGINT", pid);
-			kill(pid, SIGINT);
+			kill(pid, sig);
 			free(pid_strv[i]);
 		}
 	}