||We would like to thank Rajesh Gopakumar, Karapet Mkrtchyan, Zhenya Skvortsov and Mikhail Vasiliev for helpful discussions regarding various technical and conceptual points during the course of this and previous related work. We also thank the participants of the workshop "New Ideas in Higher Spin Gravity and Holography" at Kyung-Hee University for helpful discussions and comments. SL thanks Kyung-Hee University for hospitality during the course of this work. The work of EJ was supported by the National Research Foundation of Korea through the grant NRF2014R1A6A3A04056670. SL's research is supported by a Marie Sklodowska Curie Individual Fellowship 2014.