bugfix: set canary attributes when initializing balancer

rootfs/etc/nginx/lua/balancer/round_robin.lua

@@ -8,6 +8,8 @@ function _M.new(self, backend)
   local nodes = util.get_nodes(backend.endpoints)
   local o = {
     instance = self.factory:new(nodes),
+    traffic_shaping_policy = backend.trafficShapingPolicy,
+    alternative_backends = backend.alternativeBackends,
   }
   setmetatable(o, self)
   self.__index = self