Correctly apply selected layout on dag nodes

This commit corrects a bug in the PR branch that was caused by applying
the selected initial layout in a trial to the swapped order node list.
This was causing unexpected results when applying the circuit because
the intent was to apply it only to the original input not the reversed
input.

src/sabre_layout.rs

@@ -150,7 +150,11 @@ fn layout_trial(
             std::mem::swap(&mut dag_nodes, &mut rev_dag_nodes);
         }
     }
-    let layout_dag = apply_layout(&dag_nodes, &initial_layout, num_physical_qubits, num_clbits);
+    // Reverse the circuit back to avoid replaying the circuit in reverse order.
+    // the output of the loop above will always have the reverse order nodes set
+    // to dag_nodes. So one more swap is needed to restore the original order
+    std::mem::swap(dag_nodes, &mut rev_dag_nodes);
+    let layout_dag = apply_layout(dag_nodes, &initial_layout, num_physical_qubits, num_clbits);
     let mut final_layout = initial_layout.clone();
     let (swap_map, gate_order) = build_swap_map_inner(
         num_physical_qubits,