[cinder][qa] propose Liang Fang for devstack-plugin-open-cas-core

Liang Fang is driving the effort to create the devstack-plugin-open-cas and use it to test the cinder/nova volume-local-cache feature with tempest. Since he's our SME on open-cas, I propose that he be made a member of devstack-plugin-open-cas-core. (Currently, the only members of that group are the members of cinder-core and devstack-core.) In the absence of objections, I'll make the change before the next Cinder team meeting (Wednesday, 25 March at 1400 UTC in its new location of #openstack-meeting-alt). cheers, brian