[QOLSVC-4096] use file-based Beaker sessions for testing

- This avoids the need for a validation key

.docker/test.ini

@@ -29,6 +29,7 @@ use = egg:ckan
 full_stack = true
 cache_dir = /tmp/%(ckan.site_id)s/
 beaker.session.key = ckan
+beaker.session.type = file
 
 # This is the secret token that the beaker library uses to hash the cookie sent
 # to the client. `paster make-config` generates a unique value for this each