Really use try_imports.

Change-Id: Icad95a835ace5f75908c4c8ee0304fe528959ec3
Reviewed-on: https://review.openstack.org/17260
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Approved: Monty Taylor <mordred@inaugust.com>
Reviewed-by: Monty Taylor <mordred@inaugust.com>
Tested-by: Jenkins

zuul/cmd/server.py

@@ -19,7 +19,7 @@ import extras
 
 # as of python-daemon 1.6 it doesn't bundle pidlockfile anymore
 # instead it depends on lockfile-0.9.1 which uses pidfile.
-pid_file_module = extras.try_import(['daemon.pidlockfile', 'daemon.pidfile'])
+pid_file_module = extras.try_imports(['daemon.pidlockfile', 'daemon.pidfile'])
 
 import logging.config
 import os