Rejected shares uptick

Unfortunately, there was a slight uptick in "duplicate shares." The duplicate shares are the result of an old bug which now needs to be dealt with differently because of the changes in how miners are assigned.

We're already testing fixes for this issue, but the first fix failed and I'll try a second one tonight. In the meantime, only 2% of shares seem to be rejected, which is less than the profitability increase brought on by the changes themselves.