Two channels integration test with token only configuration

[mambelli]

Implement a two-channels integration test like #383 but using also tokens
This will be using OSG 3.6 (no GSI support in it) and a token only configuration

Steps include:

• create a working configuration
• document it
• implement an automated test

This depends on #383 completion
#384 completion could be useful as well since the token configuration will be similar