fix references to the default shard settings for rails 3

Change-Id: Ie35fd3d9255c934d29799f99596fb65e75181947
Reviewed-on: https://gerrit.instructure.com/29599
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: James Williams  <jamesw@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>

config/initializers/switchman.rb

@@ -17,6 +17,13 @@ unless CANVAS_RAILS2
     reset_column_information # make sure that the id column object knows it is the primary key
 
     serialize :settings, Hash
+    # the default shard was already loaded, but didn't deserialize it
+    if default.is_a?(self)
+      settings = ActiveRecord::AttributeMethods::Serialization::Attribute.new(serialized_attributes['settings'],
+                                                                   default.read_attribute('settings'),
+                                                                   :serialized).unserialize
+      default.settings = settings
+    end
 
     before_save :encrypt_settings