[service-vm] Send shutdown request to exit rialto

And rialto will be in a loop of processing request till receiving
the shutdown request.

Bug: 299432766
Test: atest rialto_test
Change-Id: Ifd65adde74a370a91fc462930bb513a3e1fe65b9
diff --git a/rialto/tests/test.rs b/rialto/tests/test.rs
index 20d00b5..fc6e20a 100644
--- a/rialto/tests/test.rs
+++ b/rialto/tests/test.rs
@@ -55,8 +55,8 @@
     let message = "abc".repeat(166);
     let request = Request::Reverse(message.as_bytes().to_vec());
 
-    let response = vm.process_request(&request)?;
-    info!("Received response '{response:?}' for the request '{request:?}'.");
+    let response = vm.process_request(request)?;
+    info!("Received response: {response:?}.");
 
     let expected_response: Vec<u8> = message.as_bytes().iter().rev().cloned().collect();
     assert_eq!(Response::Reverse(expected_response), response);