rootfs pin: fix two bugs

src/lxc/conf.c

@@ -578,7 +578,7 @@ int pin_rootfs(const char *rootfs)
 	int ret, fd;
 
 	if (rootfs == NULL || strlen(rootfs) == 0)
-		return 0;
+		return -2;
 
 	if (!realpath(rootfs, absrootfs)) {
 		SYSERROR("failed to get real path for '%s'", rootfs);

src/lxc/start.c

@@ -620,7 +620,8 @@ static int do_start(void *data)
 	lxc_sync_fini_parent(handler);
 
 	/* don't leak the pinfd to the container */
-	close(handler->pinfd);
+	if (handler->pinfd >= 0)
+		close(handler->pinfd);
 
 	/* Tell the parent task it can begin to configure the
 	 * container and wait for it to finish