stop sync if an invalid block was received
stop sync if an invalid block was received

RomanZacharia/pyethapp,heikoheiko/pyethapp,gsalgado/pyethapp,ethereum/pyethapp,danielnovy/test,kustomzone/pyethapp,gsalgado/pyethapp,ethereum/pyethapp,changwu-tw/pyethapp,RomanZacharia/pyethapp,d-das/pyethapp,changwu-tw/pyethapp,vaporry/pyethapp