Allow congress to run with no datasources
Allow congress to run with no datasources

Previously congress would no return cage so congress-server would
fail to start. Now it does.

Change-Id: I8ff7d7c4aee5196a11e97935e8b07669ad00834c
Closes-bug: 1395119

ramineni/my_congress,ekcs/congress,openstack/congress,ekcs/congress,openstack/congress,ramineni/my_congress,ekcs/congress,ramineni/my_congress,ekcs/congress,ramineni/my_congress