backport of ndb DictCache fix

- don't invalidate tables that are in state RETRIEVING

ndb/src/ndbapi/DictCache.cpp

@@ -278,6 +278,8 @@ GlobalDictCache::invalidate_all()
     if (vers->size())
     {
       TableVersion * ver = & vers->back();
+      if (ver->m_status != RETREIVING)
+      {
         ver->m_impl->m_status = NdbDictionary::Object::Invalid;
         ver->m_status = DROPPED;
         if (ver->m_refCount == 0)
@@ -286,6 +288,7 @@ GlobalDictCache::invalidate_all()
           vers->erase(vers->size() - 1);
         }
       }
+    }
     curr = m_tableHash.getNext(curr);
   }
   DBUG_VOID_RETURN;