The reboot-vm job needs to live off the master machine.
Note that this uses a rackspace API-key. We run tests on the non-master node and if people start the tests, they would be able to expose the API-key with a malicious test-case. You need to make sure to secure the API-key in some way or form.
This is done: http://git.gluster.org/cgit/build-jobs.git/commit/?id=519198e461ef320c346bbfce5a7d9c128e53a935