allow before_save callback for redis job to initialize defaults for rails3

Change-Id: I9da990f81835f6a9afb2ab77a5408b7532dacf3b
Reviewed-on: https://gerrit.instructure.com/29272
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: James Williams  <jamesw@instructure.com>
Product-Review: Derek DeVries <ddevries@instructure.com>
QA-Review: Derek DeVries <ddevries@instructure.com>

vendor/plugins/delayed_job/lib/delayed/backend/redis/job.rb

@@ -35,7 +35,7 @@ end
 class Job
   unless CANVAS_RAILS2
     extend ActiveModel::Callbacks
-    define_model_callbacks :create
+    define_model_callbacks :create, :save
   end
   include Delayed::Backend::Base
   # This redis instance needs to be set by the application during jobs configuration