Remove roundErrors from digest in round info

mixmessages/digesttesthelper.go

mixmessages/roundInfo.go

network/dataStructures/round.go

network/dataStructures/roundData.go

network/dataStructures/roundData_test.go

network/dataStructures/roundUpdates.go

network/dataStructures/roundUpdates_test.go

network/dataStructures/round_test.go

network/instance.go

network/instance_test.go

testutils/utils.go