Allow backends to auto-complete model transaction policy (#283)

* Added adding handling of model_transaction_policy to updateConfig for vllm backend modtly

Author: oandreeva-nv

src/backend_model.cc

@@ -693,7 +693,6 @@ TritonModel::UpdateModelConfig(
       JsonToModelConfig({buffer, byte_size}, config_version, &updated_config));
   auto config = Config();
   config.set_max_batch_size(updated_config.max_batch_size());
-
   auto inputs_config = config.mutable_input();
   *inputs_config = updated_config.input();
   auto outputs_config = config.mutable_output();
@@ -722,6 +721,12 @@ TritonModel::UpdateModelConfig(
             .c_str());
   }  // else do nothing
 
+  // Update model_transaction_policy if needed
+  if (updated_config.has_model_transaction_policy()) {
+    bool is_decoupled = updated_config.model_transaction_policy().decoupled();
+    config.mutable_model_transaction_policy()->set_decoupled(is_decoupled);
+  }
+
   // Need to normalize the model configuration for
   // populating missing fields.
   RETURN_IF_ERROR(NormalizeModelConfig(min_compute_capability_, &config));