use explicit 0.0 so sort after export works fine (respecting order)

src/debug/traces/starpu_fxt_mpi.c

@@ -235,8 +235,8 @@ static void display_all_transfers_from_trace(FILE *out_paje_file, unsigned n)
 		poti_SetVariable(0., mpi_container, "bwi_mpi", 0.);
 		poti_SetVariable(0., mpi_container, "bwo_mpi", 0.);
 #else
-		fprintf(out_paje_file, "13	%.9f	%u_mpict	bwi_mpi	%f\n", 0., node, 0.);
-		fprintf(out_paje_file, "13	%.9f	%u_mpict	bwo_mpi	%f\n", 0., node, 0.);
+		fprintf(out_paje_file, "13	0.0	%u_mpict	bwi_mpi	0.0\n", node);
+		fprintf(out_paje_file, "13	0.0	%u_mpict	bwo_mpi	0.0\n", node);
 #endif
 	}