Make SMP-awareness in MPI_Barrier consistent.
The current implementation of SMP-awareness in MPI_Barrier was in MPIR_Barrier_impl. This makes the default implementation of barrier SMP-aware. However, if a device overrides barrier and then calls back the default implementation through MPIR_Barrier, it can no longer take advantage of SMP-awareness. This patch moves the SMP-aware implementation to MPIR_Barrier_intra, which is called by MPIR_Barrier_impl through MPIR_Barrier, in the default implementation. See #1957. Signed-off-by: Michael Blocksome <firstname.lastname@example.org>