Update VM Initializer for Netbox 2.7

The vm database model has changed in Netbox 2.7.
Therefore the initializer code, that was used before, broke.
As a user, you will need to update your virtual_machines.yml
file as follows:

- Make sure the status is spelled lowercase.

See the diff of this commit for further information how this is meant.

startup_scripts/220_prefixes.py

@@ -1,6 +1,5 @@
 from dcim.models import Site
 from ipam.models import Prefix, VLAN, Role, VRF
-from ipam.constants import PREFIX_STATUS_CHOICES
 from tenancy.models import Tenant, TenantGroup
 from extras.models import CustomField, CustomFieldValue
 from ruamel.yaml import YAML
@@ -38,12 +37,6 @@ with file.open('r') as stream:
 
           params[assoc] = model.objects.get(**query)
 
-      if 'status' in params:
-        for prefix_status in PREFIX_STATUS_CHOICES:
-          if params['status'] in prefix_status:
-            params['status'] = prefix_status[0]
-            break
-
       prefix, created = Prefix.objects.get_or_create(**params)
 
       if created: