mw.Upload.BookletLayout: Move error checking for uploadToStash to uploadFile
We were checking for uploadToStash errors in saveFile, instead of in
uploadFile itself. Apart from being just wrong it was causing two
issues:
1. We would show an upload error until after you've tried to save the
file.
2. If there was an error in saving, and you try again, the first thing
it would do is check mw.Upload.State to hopefully check for
uploadToStash errors. Instead of running the finishStashUpload again
it would fail because of the earlier error, thus making all errors
unrecoverable.
Bug: T114130
Change-Id: I56f4ef6e6536840a63402688eb2a1875a6876fcc