The behavior of ompi_comm_set was changed to get the remote size from
the remote group. This broke how ompi_comm_[i]dup were using
ompi_comm_set. In order to adapt to the new behavior these functions
now pass NULL for the remote group if the communicator is not an
inter-communicator.
Signed-off-by: Nathan Hjelm <hjelmn@lanl.gov>