don't disallow deleting a section due to StudentViewEnrollments

fixes CNVS-2623

test plan:
 - create a course
 - create a section
 - use student view
 - delete the empty section
 - it should not give you a snarky message about you can't
   delete a section with enrollments

Change-Id: Ieabf6dfa6c25eed7f637d529cd755490bde5635a
Reviewed-on: https://gerrit.instructure.com/19120
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: James Williams  <jamesw@instructure.com>
QA-Review: Adam Phillipps <adam@instructure.com>
Product-Review: Jeremy Stanley <jeremy@instructure.com>

app/models/course_section.rb

@@ -213,7 +213,7 @@ class CourseSection < ActiveRecord::Base
   end
 
   def deletable?
-    self.enrollments.count == 0
+    self.enrollments.not_fake.count == 0
   end
 
   def enroll_user(user, type, state='invited')

spec/models/course_section_spec.rb

@@ -247,4 +247,25 @@ describe CourseSection, "moving to new course" do
     CourseAccountAssociation.find_all_by_course_id(course2.id).map(&:account_id).uniq.sort.should == [account1.id, account2.id].sort
   end
   
+  describe 'deletable?' do
+    before do
+      course_with_teacher
+      @section = course.course_sections.create!
+    end
+    
+    it 'should be deletable if empty' do
+      @section.should be_deletable
+    end
+    
+    it 'should not be deletable if it has real enrollments' do
+      student_in_course :section => @section
+      @section.should_not be_deletable
+    end
+    
+    it 'should be deletable if it only has a student view enrollment' do
+      @course.student_view_student
+      @section.enrollments.map(&:type).should eql ['StudentViewEnrollment']
+      @section.should be_deletable
+    end
+  end
 end