conf: Ignore the volume type disk if its mode is "direct"

virDomainDiskDefForeachPath is not only used by the security
setting helpers, also used by cgroup setting helpers, so this
is to ignore the volume type disk with mode="direct" for cgroup
setting.

src/conf/domain_conf.c

@@ -17533,7 +17533,10 @@ virDomainDiskDefForeachPath(virDomainDiskDefPtr disk,
     size_t depth = 0;
     virStorageFileMetadata *tmp;
 
-    if (!disk->src || disk->type == VIR_DOMAIN_DISK_TYPE_NETWORK)
+    if (!disk->src || disk->type == VIR_DOMAIN_DISK_TYPE_NETWORK ||
+        (disk->type == VIR_DOMAIN_DISK_TYPE_VOLUME &&
+         disk->srcpool &&
+         disk->srcpool->mode == VIR_DOMAIN_DISK_SOURCE_POOL_MODE_DIRECT))
         return 0;
 
     if (iter(disk, disk->src, 0, opaque) < 0)