workflow_state is a string, not a symbol

Change-Id: I4d7d10ae0e33a5d84c39a35fcbb0ec21f366cf4c
Reviewed-on: https://gerrit.instructure.com/5220
Tested-by: Hudson <hudson@instructure.com>
Reviewed-by: Zach Wily <zach@instructure.com>

db/migrate/20110822151806_remove_inactive_enrollment_state.rb

@@ -1,7 +1,7 @@
 class RemoveInactiveEnrollmentState < ActiveRecord::Migration
   def self.up
     Delayed::Job.delete_all(:tag => 'EnrollmentDateRestrictions.update_restricted_enrollments')
-    Enrollment.update_all({:workflow_state => :active}, :workflow_state => :inactive)
+    Enrollment.update_all({:workflow_state => 'active'}, :workflow_state => 'inactive')
   end
 
   def self.down