ListField(CachedReferenceField) does not auto sync

Extending on #1560 I discovered that Lists of CachedReferenceField do not receive the updates to the cached fields when the master record is updated.

from mongoengine import *
from mongoengine.connection import get_db
from mongoengine.base import (BaseDict, BaseField, EmbeddedDocumentList,
                              _document_registry)



class Owner(EmbeddedDocument):
    name = StringField()
    tags = ListField(StringField())

class Animal(Document):
    name = StringField()
    tag = StringField()

    owner = EmbeddedDocumentField(Owner)

class Ocorrence(Document):
    person = StringField()
    animal = ListField(CachedReferenceField(
        Animal, fields=['tag', 'owner.tags']))

Animal.drop_collection()
Ocorrence.drop_collection()

a = Animal(name="Leopard", tag="heavy",
           owner=Owner(tags=['cool', 'funny'],
                       name="Wilson Júnior")
           )
a2 = Animal(name="Tiger", tag="too heavy",
           owner=Owner(tags=['cool2', 'funny2'],
                       name="Wilson")
           )
a.save()
a2.save()

o = Ocorrence(person="teste 2", animal=[a,a2])
o.save()
a.tag="Very Heavy"
a.save()

Start by reproducing the provided example with ListField(CachedReferenceField) and trace how CachedReferenceField updates are handled for list references. Done means updating and saving the master Animal refreshes the corresponding cached fields in the Ocorrence.animal list.