replay: pass `mpi_comm`
Blueprints such as this support passing mpi communicator via mpi_comm. When replaying, however, this mpi_comm is invalid. we need to replace it by the actual MPI communicator during replay.
Blueprints such as this support passing mpi communicator via mpi_comm. When replaying, however, this mpi_comm is invalid. we need to replace it by the actual MPI communicator during replay.