Synchronization tweaks for IPC services (#2028)

* using sequentally consistent checks

* making shutdown method synchronous

* redndant line

ipc/hypervisor/src/service.rs.in

@@ -42,7 +42,7 @@ pub struct ModuleState {
 
 #[derive(Ipc)]
 pub trait ControlService {
-	fn shutdown(&self);
+	fn shutdown(&self) -> bool;
 }
 
 #[derive(Ipc)]