minor changes for checking if rhs is to be reused
minor changes for checking if rhs is to be reused

zasdfgbnm/qutip,anubhavvardhan/qutip,qutip/qutip,cgranade/qutip,anubhavvardhan/qutip,zasdfgbnm/qutip,qutip/qutip,cgranade/qutip