don't copy integration id/data when duplicating assignment

closes #CNVS-39616

Change-Id: Ifcad21acef66f0f2adb65a795be0ff43e162dd93
Reviewed-on: https://gerrit.instructure.com/127718
Tested-by: Jenkins
Reviewed-by: Rob Orton <rob@instructure.com>
Product-Review: James Williams  <jamesw@instructure.com>
QA-Review: James Williams  <jamesw@instructure.com>

app/models/assignment.rb

@@ -158,14 +158,14 @@ class Assignment < ActiveRecord::Base
     opts_with_default = default_opts.merge(opts)
 
     result = self.clone
-    result.migration_id = nil
     result.all_submissions.clear
     result.attachments.clear
     result.ignores.clear
     result.moderated_grading_selections.clear
-    result.lti_context_id = nil
-    result.turnitin_id = nil
-    result.discussion_topic = nil
+    [:migration_id, :lti_context_id, :turnitin_id,
+      :discussion_topic, :integration_id, :integration_data].each do |attr|
+      result.send(:"#{attr}=", nil)
+    end
     result.peer_review_count = 0
     result.workflow_state = "unpublished"
     # Default to the last position of all active assignments in the group.  Clients can still