fix switchman settings initialization for rails 3

Change-Id: I926d13c5ce839e7236d8e2c7720be01e5e044eea
Reviewed-on: https://gerrit.instructure.com/29530
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Cody Cutrer <cody@instructure.com>
Product-Review: James Williams  <jamesw@instructure.com>
QA-Review: James Williams  <jamesw@instructure.com>

config/initializers/switchman.rb

@@ -20,10 +20,11 @@ unless CANVAS_RAILS2
 
     def settings
       s = super
+      unless s.is_a?(Hash) || s.nil?
+        s = s.unserialize
+      end
       if s.nil?
         self.settings = s = {}
-      elsif !s.is_a?(Hash)
-        s = s.unserialize
       end
 
       salt = s.delete(:encryption_key_salt)