Add GDS metrics package to admin app

Follows the code from the API

gunicorn_config.py

@@ -4,6 +4,8 @@ import traceback
 
 import gunicorn
 
+from gds_metrics.gunicorn import child_exit  # noqa
+
 workers = 5
 worker_class = "eventlet"
 errorlog = "/home/vcap/logs/gunicorn_error.log"