initctl: ignore possibly missing cpu.stat in cgroup2 root

Older kernels (4.19) don't have the summary cpu.stat in the cgroup2
root, so let's ignore that problem and return zero.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

src/cgutil.c

@@ -231,7 +231,9 @@ static struct cg *append(char *path)
 
 	snprintf(fn, sizeof(fn), "%s/cpu.stat", path);
 	if (access(fn, F_OK)) {
-		warn("not a cgroup path with cpu controller, %s", path);
+		/* older kernels, 4.19, don't have summary cpu.stat in root */
+		if (strcmp(path, FINIT_CGPATH))
+			warn("not a cgroup path with cpu controller, %s", path);
 		return NULL;
 	}