## Bug description
- See screenshot below (it's likely being processed in 3 workers at the same time).

![sc](https://user-images.githubusercontent.com/5864173/92016443-f6457800-ed17-11ea-9b7f-959a3306850e.png)


## Expected behavior
- We should receive the event only once.


## How to reproduce

1. View a user of recent creation with this event ([example](https://app.posthog.com/person/5fabb7b9-a36c-4419-af97-eea75960b2e4)) 

## Environment

- Cloud from PR #1508 

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

posthog/celery.py
try:
        g = statsd.Gauge("%s_posthog_celery" % (settings.STATSD_PREFIX,))
        llen = get_client().llen("celery")
        g.send("queue_depth", llen)
    except:
        
        
        return
@app.task(ignore_result=True)
def update_event_partitions():
    with connection.cursor() as cursor:
        cursor.execute(
            "DO $$ BEGIN IF (SELECT exists(select * from pg_proc where proname = 'update_partitions')) THEN PERFORM update_partitions(); END IF; END $$"
        )
@app.task(ignore_result=True)
def clean_stale_partials():
    """Clean stale (meaning older than 7 days) partial social auth sessions."""
    from social_django.models import Partial
    Partial.objects.filter(timestamp__lt=timezone.now() - timezone.timedelta(7)).delete()
@app.task(ignore_result=True)
def status_report():
    from posthog.tasks.status_report import status_report
    status_report()
@app.task(ignore_result=True)
def run_session_recording_retention():