Use inspect when writing the foreign key from the reflection

If we don't use inspect inside the class_eval block then the foreign key
is written without quotes causing us to fetch the foreign key value and
not the column name.

activerecord/lib/active_record/associations/builder/belongs_to.rb

@@ -68,11 +68,11 @@ def add_touch_callbacks(reflection)
         def belongs_to_touch_after_save_or_destroy_for_#{name}
           record = #{name}
 
-          foreign_key_field   = #{reflection.foreign_key}
+          foreign_key_field   = #{reflection.foreign_key.inspect}
           if changed_attributes.key?(foreign_key_field)
             reflection_klass  = #{reflection.klass}
             old_foreign_id    = changed_attributes[foreign_key_field]
-            old_record        = reflection_klass.where(foreign_key_field.to_sym => old_foreign_id).first
+            old_record        = reflection_klass.where(foreign_key_field => old_foreign_id).first
             if old_record
               old_record.touch #{options[:touch].inspect if options[:touch] != true}
             end

activerecord/test/cases/timestamp_test.rb

@@ -192,6 +192,12 @@ def self.name; 'Toy'; end
     old_pet.update_columns(updated_at: time)
     new_pet.update_columns(updated_at: time)
 
+    old_pet.reload
+    new_pet.reload
+
+    assert_equal time, new_pet.updated_at
+    assert_equal time, old_pet.updated_at
+
     toy1.pet = new_pet
     toy1.save!