Fix preservation of ListOp's combofn (Qiskit/qiskit-aqua#1152)
Fix preservation of ListOp's combofn (Qiskit/qiskit-aqua#1152)

* propagate value of combo_fn

* fix combo fn in listop

* fix mypy warnings

* use explicit args instead of **state

Co-authored-by: Steve Wood <df319c8b10182f101be29ecf0d4d148dec6c4bfc@users.noreply.github.com>
QISKit/qiskit-sdk-py,QISKit/qiskit-sdk-py,QISKit/qiskit-sdk-py