[FIX] mail: mark a message as read should not hide 'load more' button

It was hidding it because the method that removes a message from the thread
didn't pass the options for the thread rendering, and the flag specifiying
whether or not the 'load more' button should be displayed is in this options
object.

addons/mail/static/src/js/client_action.js

@@ -409,7 +409,8 @@ var ChatAction = Widget.extend(ControlPanelMixin, {
         if ((this.channel_id === "channel_starred" && !message.is_starred) ||
             (this.channel_id === "channel_inbox" && !message.is_needaction)) {
             chat_manager.fetch(this.channel_id, this.domain).then(function (messages) {
-                self.thread.remove_message_and_render(message.id, messages);
+                var options = {display_load_more: !chat_manager.all_history_loaded(self.channel_id)};
+                self.thread.remove_message_and_render(message.id, messages, options);
             });
         } else if (_.contains(message.channel_ids, this.channel_id)) {
             this.fetch_and_render_thread();

addons/mail/static/src/js/thread.js

@@ -91,11 +91,12 @@ var Thread = Widget.extend({
      * Removes a message and re-renders the thread
      * @param {int} [message_id] the id of the removed message
      * @param {array} [messages] the list of messages to display, without the removed one
+     * @param {object} [options] options for the thread rendering
      */
-    remove_message_and_render: function (message_id, messages) {
+    remove_message_and_render: function (message_id, messages, options) {
         var self = this;
         this.$('.o_thread_message[data-message-id=' + message_id + ']').fadeOut({
-            done: function () { self.render(messages); }
+            done: function () { self.render(messages, options); }
         });
     },