Should show some progress indicator during upload md5 calculation

Prior to initiating a file upload the client calculates the md5 for the file. For a large file (e.g. 10s of GBs) this can take minutes during which time the client does not produce any output and appears hung. Console output appears once the file transfer initiates with the transfer progress bar, after the md5 calculation. We should show some output while calculating the md5.

The md5 calculation itself is a blocking call, and it would be difficult to produce some sensible measure of how long it would take relative to the file transfer, but likely just a placebo spinning cursor or similar would be enough to allay a fear that the client was hung.

Noticed this in an RC for 2.1 but this is not a regression and exists in prior versions as well.