Fix a race with replicainfo update for the same checkpoint because of checkpoint open or replica intimation delays that results in a race where 1 thread ends up deleting the checkpoint before updating the replica while another thread updates the info. for the checkpoint obtained from the active replica. The race stems from the fact, that the ckpt mutex could be created after the deleting thread frees up the ckpt info. The fix ensures that we hold the ckpt global activeSem till the ckpt mutex is created before dropping it. Closes Issue #42