Make QueryCustomers behave appropriate for querying updates to customers

Currently the trigger is using the following parameters on first run.

```
{ where: [ 'lastModifiedAt > "1970-01-01T00:00:00.000Z" and externalId is defined' ],
  operator: 'and',
  sort: [],
  expand: [] }
```

If you configured Query Customers trigger to sync customer's update, the trigger might produce unexpected results as it will query all customers, even if they where not updated.
