orgs_controller#shibboleth_ds: redirect should return

[nicolasfranck]

Please complete the following fields as applicable:

Expected behaviour:

Actual behaviour:

Rails complains that rendering happens twice.

Reason: https://github.com/DMPRoadmap/roadmap/blob/master/app/controllers/orgs_controller.rb#L88

The redirect does not issue a return from the function shibboleth_ds and therefore
https://github.com/DMPRoadmap/roadmap/blob/master/app/controllers/orgs_controller.rb#L96 is executed also.

Steps to reproduce:

• checkout version 2.2.0
• login
• make sure there are no organisations with a shibboleth scheme identifier
• go to /orgs/shibboleth