give up on refactoring TestFileUpload
give up on refactoring TestFileUpload

The reason that t.Parallel broke the tests was because the parent test
must finish before the parallel subtests can start. So, we'd be closing
the httptest server and removing the tmpfile before any of the parallel
subtests even began.

We could refactor this to make the subtests parallel, but they're only
two, and the parent is already parallel, so it's not worth the effort.
See the added comment.

knq/chromedp,chromedp/chromedp,chromedp/chromedp,knq/chromedp,knq/chromedp,chromedp/chromedp