Designate DNS – the default SOA and NS recordsets are counted for quota

The default created SOA and NS recordsets for a Zone are counted in quota, but shouldn't.
We should only count stuffs that is created by user.

Test scenario:
1) Set quotas for a user with:
quotas = {
    'zones': 7, 'zone_recordsets': 1, 'zone_records': 7,
    'recordset_records': 7, 'api_export_size': 7}

2) Try to create a Zone

Expected Result:
Zone is sucsesfully created

Actual result:
Zone creation fails on:
Details: {'code': 413, 'type': 'over_quota', 'message': 'Quota exceeded for zone_recordsets.', 'request_id': 'req-0a7f59a6-7c06-42dc-b6fd-6ae4d78e2cc6'}