fix(update-agent): flush the capsule to disk (#1332)

-- Tiny fix: ensure that data is sync'ed to disk before moving on

Author: sfikastheo

update-agent/src/update/capsule.rs

@@ -86,6 +86,7 @@ where
         .create_file(CAPSULE_INSTALL_NAME)
         .map_err(|e| Error::CreateFile(e, CAPSULE_INSTALL_NAME.into()))?;
     io::copy(&mut src, &mut capsule).map_err(Error::CopyCapsule)?;
+    capsule.sync_all().map_err(Error::CopyCapsule)?;
     Ok(())
 }