evolve: delete dead calculation of number of troubled revisions The "count" variable is recalculated in the regular (no --continue) code path and it isn't used anywhere else (it used to be set to 1 in the --continue code path, but that now has its own progress counting).

evolve: drop nested locks and transactions All callers of _solveone() now take the locks and start the transactions, so there's no need to do that anymore.