make MPI_Send and MPI_Recv Fault Tolerant

```MPI_Send``` and ```MPI_Recv``` are not sending concurrent data from ```replica_sender -> compute_receiver``` and ```replica_sender -> replica_receiver```. So in case of ```compute_sender``` failure ```err_handler``` is not getting invoked and some other rank do the ```MPI_Comm_shrink``` from which ```replica_sender``` is automatically neglected. 

This isn't the way it should work.