Fix a bunch of false "File sent" logs (and uploader-notifications)

Web browsers tend start a download and then immediately close the socket
(so now send_failed will be true), while on a secondary socket, do a range
download of the same file.

So log the range requests/completions and don't log successful file sends
when the send was terminated due to a send failure.

We still count very small (e.g. 2 byte) ranges as successful file transfers
and notify the uploader (of a partial download), so we should fix those
issues still. But at least now, there's a whole lot less "noise" created
from HTTP[S} file downloads via browser.