课程allow_join方法增加课程的传入，减少课程获取次数

app/controllers/courses_controller.rb

@@ -29,7 +29,7 @@ class CoursesController < ApplicationController
       if course
         @state = 4
       else
-        unless (allow_join && User.current.member_of_course?(course))
+        unless (allow_join(course) && User.current.member_of_course?(course))
           if params[:course_password] == course.password
             members = []
             members << Member.new(:role_ids => [10], :user_id => User.current.id)
@@ -700,8 +700,8 @@ class CoursesController < ApplicationController
 
   private
 
-  def allow_join
-    if course_endTime_timeout? Course.find(params[:object_id])
+  def allow_join course
+    if course_endTime_timeout? course
       respond_to do |format|
         format.js {
           @state = 2