Do IfElseOp test without builder interface

Before, we used the builder interface for an ifelse op. Some details of
the circuit built, in particular the mapping of wires is not deterministic.
We could have used canonicalize_control_flow. But instead we construct the
IfElseOp manually. This removes the complexity of the builder interface from
this test.

test/python/transpiler/test_consolidate_blocks.py

@@ -16,8 +16,9 @@
 
 import unittest
 import numpy as np
+import copy
 
-from qiskit.circuit import QuantumCircuit, QuantumRegister
+from qiskit.circuit import QuantumCircuit, QuantumRegister, IfElseOp
 from qiskit.circuit.library import U2Gate, SwapGate, CXGate
 from qiskit.extensions import UnitaryGate
 from qiskit.converters import circuit_to_dag
@@ -430,7 +431,7 @@ def test_identity_1q_unitary_is_removed(self):
 
     def test_descent_into_control_flow(self):
         """Test consolidation in blocks of control flow op is the same as at top level."""
-        qc = QuantumCircuit(2)
+        qc = QuantumCircuit(2, 1)
         u2gate1 = U2Gate(-1.2, np.pi)
         u2gate2 = U2Gate(-3.4, np.pi)
         qc.append(u2gate1, [0])
@@ -444,11 +445,16 @@ def test_descent_into_control_flow(self):
         result_top = pass_manager.run(qc)
 
         qc_control_flow = QuantumCircuit(2, 1)
-        with qc_control_flow.if_test((0, False)):
-            qc_control_flow.append(u2gate1, [0])
-            qc_control_flow.append(u2gate2, [1])
-            qc_control_flow.cx(0, 1)
-            qc_control_flow.cx(1, 0)
+        qc_block = copy.deepcopy(qc)
+
+        qc_block = QuantumCircuit(qc.qubits, qc.clbits)
+        qc_block.append(u2gate1, [0])
+        qc_block.append(u2gate2, [1])
+        qc_block.cx(0, 1)
+        qc_block.cx(1, 0)
+
+        ifop = IfElseOp((qc.clbits[0], False), qc_block, None)
+        qc_control_flow.append(ifop, qc.qubits, qc.clbits)
 
         pass_manager = PassManager()
         pass_manager.append(Collect2qBlocks())