Make binder status update callbacks one-way

We don't need to synchronize with every single client. This might have
some modest performance implications.

TEST=Verified update_engine_client commands still work
Bug: None

Change-Id: If66d9be4b2835b175139f484cee916fc5212185d
diff --git a/binder_bindings/android/brillo/IUpdateEngineStatusCallback.aidl b/binder_bindings/android/brillo/IUpdateEngineStatusCallback.aidl
index 385e0aa..42b6438 100644
--- a/binder_bindings/android/brillo/IUpdateEngineStatusCallback.aidl
+++ b/binder_bindings/android/brillo/IUpdateEngineStatusCallback.aidl
@@ -17,6 +17,7 @@
 package android.brillo;
 
 interface IUpdateEngineStatusCallback {
+  oneway
   void HandleStatusUpdate(in long last_checked_time, in double progress,
       in String current_operation, in String new_version, in long new_size);
 }