Revert r28544: the original code was fine.

This commit was SVN r28549.

The following SVN revision numbers were found above:
  r28544 --> open-mpi/ompi@c830d96673

ompi/mpi/cxx/op_inln.h

@@ -145,5 +145,5 @@ MPI::Op::Is_commutative(void) const
 {
     int commute;
     (void)MPI_Op_commutative(mpi_op, &commute);
-    return (bool) (commute != 0);
+    return (bool) commute;
 }