validate UPDATE do not validate empty obsolete container

Fixes CESNET#2370

Author: jeremie6wind

src/validation.c

@@ -1621,7 +1621,8 @@ lyd_validate_obsolete(const struct lyd_node *node)
 
     snode = node->schema;
     do {
-        if (snode->flags & LYS_STATUS_OBSLT) {
+        if (snode->flags & LYS_STATUS_OBSLT &&
+            (!(snode->nodetype & LYD_NODE_INNER) || lyd_child(node))) {
             LOG_LOCSET(NULL, node);
             LOGWRN(snode->module->ctx, "Obsolete schema node \"%s\" instantiated in data.", snode->name);
             LOG_LOCBACK(0, 1);