_resync method bug

[AlbertoNieto44]

When using the context manager not_computed, the _resync method does not properly compute the fields update fields.

Implications:

Case 1: Model with a computed field which is not updated triggers the update of all related dependencies.

class ModelA(ComputedFieldsModel, models.Model):
    field_1 = models.FloatField()
    field_2 = models.FloatField()
    @computed(
        models.FloatField(),
        depends=[['self', ['field_1', 'field_2']]])
    def computed_field(self):
        return func(field_1, field_2)

class ModelB(ComputedFieldsModel, models.Model):
    m2m_field = models.ManyToManyField('modelA')

    @computed(
      models.FloatField(),
      depends=[
          ['m2m_field', ['id']],
      ])
    def computed_field(self):
        return func(self.m2m_field)

In this case, we write modelA.save(update_fields=['field_1']) and all records of modelB are recomputed

Case 2: Update of dependent model not being triggered.

class ModelA(ComputedFieldsModel, models.Model):
    field_1 = models.FloatField()
    @computed(
        models.FloatField(),
        depends=[['self', ['field_1']]])
    def computed_field(self):
        return func(field_1)

class ModelB(ComputedFieldsModel, models.Model):
    m2m_field = models.ManyToManyField('modelA')

    @computed(
      models.FloatField(),
      depends=[
          ['m2m_field', ['field_1']],
      ])
    def computed_field(self):
        return func(self.m2m_field.field_1)

In this case, we write modelA.save(update_fields=['field_1']) and modelB is not computed