Issue READONLY as part of the client connection

Fix: #1017

Author: byroot

lib/redis/client.rb

@@ -126,6 +126,8 @@ def connect
             call [:auth, password]
           end
         end
+
+        call [:readonly] if @options[:readonly]
         call [:select, db] if db != 0
         call [:client, :setname, @options[:id]] if @options[:id]
         @connector.check(self)

lib/redis/cluster/node.rb

@@ -76,8 +76,9 @@ def build_clients(options)
         clients = options.map do |node_key, option|
           next if replica_disabled? && slave?(node_key)
 
+          option = option.merge(readonly: true) if slave?(node_key)
+
           client = Client.new(option)
-          client.call(%i[readonly]) if slave?(node_key)
           [node_key, client]
         end