## Bug description

This is what a default feature flag looks like:
<img width="577" alt="empty feature flag" src="https://user-images.githubusercontent.com/4550621/113333154-63f36a00-9322-11eb-8fb0-71b0cd865181.png">
It has no rollout percentage specified, nor filters, so it says "Rolling out to 100% of users". However I've experienced that in fact in this situation the flag is rolled out to *nobody*.

CC @paolodamico 

## Expected behavior

Flag should work the way it says.

## How to reproduce

1. Create a feature flag and leave it as is, supposedly completely rolled out.
2. Try to use it.
3. Discover that the flag is not rolled out.

## Environment

- [x] PostHog Cloud
- [x] self-hosted PostHog, version/commit: master (8f4ae2b)

#### *Thank you* for your bug report – we love squashing them!

posthog/test/test_feature_flag.py
Person.objects.create(team=self.team, distinct_ids=["example_id"], properties={"$some_prop": "something"})
        cohort = Cohort.objects.create(
            team=self.team, groups=[{"properties": {"$some_prop": "something"}}], name="cohort1"
        )
        cohort.calculate_people(use_clickhouse=False)
        feature_flag = self.create_feature_flag(
            filters={"properties": [{"key": "id", "value": cohort.pk, "type": "cohort"}],}
        )
        self.assertTrue(feature_flag.distinct_id_matches("example_id"))
        self.assertFalse(feature_flag.distinct_id_matches("another_id"))
    def create_feature_flag(self, **kwargs):
        return FeatureFlag.objects.create(
            team=self.team, name="Beta feature", key="beta-feature", created_by=self.user, **kwargs
        )