CAS2 authentication of Administrator breaks Nuxeo Drive

1. create a CAS2 Nuxeo configuration
2. add Drive to the Nuxeo configuration and boot Nuxeo
3. create an ordinary members user "test" password "test"
4. login as CAS2 test user
5. add a synchronisation root for this test user using a browser
6. on Nuxeo Drive client-side, configure the test user => entrer URL of Nuxeo and in the same browser then before, the SSO works fine
   ==> Drive client is functional for the test user
7. log out from test in the browser and log in as Administrator
8. add a synchronisation root for this Administrator user using a browser
9. on Nuxeo Drive client-side, configure the Administrator user => entrer URL of Nuxeo and in the same browser than before, the SSO works fine
   ==> Drive client dies.

Request to fix Administrator CAS2 login breaking Drive client.