Migrating solum gate to F20

Solum is currently not compatible with Trusty's rabbitmq. While solum
debugs this run their devstack tests on Fedora 20 and run the test on
Trusty as non voting so that the issue can be debugged.

Change-Id: I5b9454c0e22e9a07492dacb0ce8c17b9584dcae5
Merge "Migrating solum gate to F20"