timm_dealloc(): fix handling of tuples that reference timm_oom

A given status tuple may contain another status tuple as value for
one of its attributes (e.g. when a status tuple is generated via a
call to `timm_up()`), and the inner tuple can be an arbitrary
tuple, including `timm_oom` (i.e. the global tuple that is
allocated during kernel initialization and is used to indicate
out-of-memory conditions). The `timm_oom` tuple must never be
deallocated, but the existing code deallocates it if it is the
value for an attribute of an outer status tuple.
This change fixes the above issue.

src/runtime/tuple.c

@@ -263,10 +263,23 @@ tuple timm_clone(tuple t)
     return (t != INVALID_ADDRESS) ? t : timm_oom;
 }
 
+closure_function(1, 2, boolean, timm_dealloc_each,
+                 tuple, t,
+                 value s, value v)
+{
+    if (tagof(v) == tag_string)
+        deallocate_string((string)v);
+    else
+        timm_dealloc((tuple)v);
+    return true;
+}
+
 void timm_dealloc(tuple t)
 {
-    if ((t != STATUS_OK) && (t != timm_oom))
-        destruct_value(t, true);
+    if ((t != STATUS_OK) && (t != timm_oom)) {
+        iterate(t, stack_closure(timm_dealloc_each, t));
+        deallocate_table(&t->t);
+    }
 }
 
 // header: immediate(1)