Don’t ask for organisation type when we know it

Every time someone adds a new service we ask them what kind of
organisation they work for.

We can look this up based on the user’s email address now. So we should
only ask the question if:
- we don’t know about the organisation
- or we haven’t set what type of organisation it is (this shouldn’t be
  possible on productions because we’ve populated the column for all
  existing organisations and it’s impossible to add a new one without
  setting it

tests/__init__.py

@@ -194,6 +194,7 @@ def organisation_json(
     domains=None,
     crown=True,
     agreement_signed=False,
+    organisation_type='',
 ):
     if users is None:
         users = []
@@ -208,7 +209,7 @@ def organisation_json(
         'created_at': created_at or str(datetime.utcnow()),
         'email_branding_id': email_branding_id,
         'letter_branding_id': letter_branding_id,
-        'organisation_type': '',
+        'organisation_type': organisation_type,
         'crown': crown,
         'agreement_signed': agreement_signed,
         'agreement_signed_at': None,