Fix missing willUpload hook for drag-and-drop chunked upload

Summary:
Ref T9324. When you upload a normal file, we call willUpload and then didUpload.

When you upload a chunked file, we never call willUpload. This can get things out of sync. Make sure we invoke this event for both chunked and non-chunked uploads.

Test Plan: Got cleaner behavior (redirect after all uploads finish) in new Phacility file upload area.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T9324

Differential Revision: https://secure.phabricator.com/D14083