Explicitly draw progress bar when resuming file uploads in arc upload

Summary: Ref T7149. Make sure we sit at "Resuming: 60%" or whatever while uploading the first chunk.

Test Plan: Ran arc upload on a large file, cancelled it, resumed it, got sensible progress bar.

Reviewers: chad, btrahan

Reviewed By: chad, btrahan

Subscribers: epriestley

Maniphest Tasks: T7149

Differential Revision: https://secure.phabricator.com/D12082