start: backport monitor_pid handling

src/lxc/start.c

@@ -769,6 +769,8 @@ int lxc_init(const char *name, struct lxc_handler *handler)
 	const char *loglevel;
 	struct lxc_conf *conf = handler->conf;
 
+	handler->monitor_pid = lxc_raw_getpid();
+
 	lsm_init();
 	TRACE("Initialized LSM");
 

src/lxc/start.h

@@ -102,6 +102,9 @@ struct lxc_handler {
 	/* The child's pid. */
 	pid_t pid;
 
+	/* The monitor's pid. */
+	pid_t monitor_pid;
+
 	/* Whether the child has already exited. */
 	bool init_died;