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'
the test method canvas_replacement, render_replacement do not match the patch statements  @patch('add_people.views.get_list_sections'), @patch('add_people.views.logger.error')