Feature/sections sapna unittests

Fixed unit tests for create_section_form, get_enrollments_without_test_student , remove_section and created separate test files for these. Also added new test casesin these methods for the new utilities 'check_resource_link_id' and 'validate_course_id'
This is again a confusing description. I think the author meant to say that when error=false(meaning everything works) then render the correct view. Fixing the description.