DrServer task scheduling favors first connected harvester

[drnick23]

Currently, when a DrSolver is finished a task, the DrServer checks the list of harvesters and gets the next task from the first harvester, then if that's empty, the 2nd harvester, etc. Tasks are ordered as FIFO for each harvester, but connecting multiple harvesters then favors tasks completion on the first harvester rather than evenly distributing FIFO across all tasks from harvesters.

[rkroelin]

I'm seeing the results of this more often now that I've stood up 5 harvesters to try and work around the banning issue. Trending the times from the drserver often shows the favoritism unless you throw a large % of extra GPU at it.