Fixed bug on Course model

getOrCreateSeat was calling a property when it should have been calling a method.

XCOM-520

ecommerce/static/js/models/course_model.js

@@ -160,10 +160,9 @@ define([
                     products = this.get('products'),
                     seat = products.find(function (product) {
                         // Filter out parent products since there is no need to display or modify.
-                        return (product instanceof CourseSeat) && (product.seatType === seatType);
+                        return (product instanceof CourseSeat) && (product.getSeatType() === seatType);
                     });
 
-                // Do NOT create new audit seats
                 if (!seat) {
                     seatClass = CourseUtils.getCourseSeatModel(seatType);
                     /*jshint newcap: false */

ecommerce/static/js/models/course_seats/course_seat.js

@@ -14,10 +14,6 @@ define([
             },
 
             validation: {
-                // TODO Determine how to set this to the model's default.
-                //certificate_type: {
-                //    required: true
-                //},
                 price: {
                     required: true
                 },