filter out test jobs from the GET /service/{}/job endpoint

this is so that the filtering, which we do on the admin side, is applied
before pagination - so that the pages returned are all valid displayable
jobs. unfortunately this means that another config value has to be copied
to the server side but it's not the end of the world

config.py

@@ -57,6 +57,7 @@ class Config(object):
     PAGE_SIZE = 50
     SMS_CHAR_COUNT_LIMIT = 495
     BRANDING_PATH = '/static/images/email-template/crests/'
+    TEST_MESSAGE_FILENAME = 'Test message'
 
     NOTIFY_SERVICE_ID = 'd6aa2c68-a2d9-4437-ab19-3ae8eb202553'
     INVITATION_EMAIL_TEMPLATE_ID = '4f46df42-f795-4cc4-83bb-65ca312f49cc'