What if there are two aux cxns on the master controller? Only one will have `cxn->cxn_id == master_id`. If that one is iterated over first, then the second one will set `cxn->controller->role = INDIGO_CXN_R_SLAVE`.

I think this loop should be done over controllers, not conenctions. The role status message can be sent to the first aux cxn.