Exclude latest outcome import from content reset

closes OUT-2370

test plan:
  - create a new, published course
  - import the CSV attached in JIRA (ignore the error message)
  - in settings, attempt to reset course content
  - ensure that the reset doesn't fail with a page error

Change-Id: Ied1763f90c9d7861eb3e0b8efbbd7ebf37f2a4d1
Reviewed-on: https://gerrit.instructure.com/172760
Tested-by: Jenkins
Reviewed-by: Neil Gupta <ngupta@instructure.com>
QA-Review: Dariusz Dzien <ddzien@instructure.com>
Product-Review: Augusto Callejas <acallejas@instructure.com>

app/models/course.rb

@@ -2904,7 +2904,7 @@ class Course < ActiveRecord::Base
   def reset_content
     Course.transaction do
       new_course = Course.new
-      self.attributes.delete_if{|k,v| [:id, :created_at, :updated_at, :syllabus_body, :wiki_id, :default_view, :tab_configuration, :lti_context_id, :workflow_state].include?(k.to_sym) }.each do |key, val|
+      self.attributes.delete_if{|k,v| [:id, :created_at, :updated_at, :syllabus_body, :wiki_id, :default_view, :tab_configuration, :lti_context_id, :workflow_state, :latest_outcome_import_id].include?(k.to_sym) }.each do |key, val|
         new_course.write_attribute(key, val)
       end
       new_course.workflow_state = (self.admins.any? ? 'claimed' : 'created')

spec/models/course_spec.rb

@@ -1041,6 +1041,8 @@ describe Course do
       profile.save!
       @course.save!
       @course.reload
+      @course.update!(latest_outcome_import:
+        OutcomeImport.create!(context: @course))
 
       expect(@course.course_sections).not_to be_empty
       expect(@course.students).to eq [@student]