lr/sc reservation set issue with handcar

Hi

The implemeation of handcar single step function has a bug: 1.handcar/fpix will single step one instruction per hart and then switch to signle step the other hart 2.spike implementation will execute a chunk of instruction(say 5000 instructions per chunk) and then clear reservation set before switch to the other hart

It seems handcar step function should check the reservation set of other cores and clear local core's reservation set if it has set action in this step.