Adds Openstack as one of the available backend for Travis jobs.
Adds Openstack as one of the available backend for Travis jobs.

- Uses gophercloud sdk to invoke Openstack compute services in addition to keystone, image and network.

- Supports keypair creation at runtime or using existing keys or password for VM (ssh)login.

- Requires Network to be pre created to be used for booting up VMs.

- Supports both v2.0 and v3 version of keystone API.

travis-ci/worker,travis-ci/worker,travis-ci/worker