listspots: show spot status and status message
awsutils: use progressbar in wait_for_propagation
cluster: always wait for propagation after launch

* Updated the _create_flat_rate_cluster and _create_spot_cluster methods
  to always wait for instance and spot request propagation regardless of
  cluster_size (ie not just when cluster_size>1).
* Minor refactor of master node launch code in _create_flat_rate_cluster
cluster: improve wait_for_active_spots

Require active spots to also have an instance_id allocated before
exiting the wait loop. This ensures that the spot requests are 'active'
and also have an instance ID that we can use in the
'wait_for_propagation' call later on. This *might* fix
InstanceDoesNotExist errors related to eventual consistency when using
spot nodes (gh-377).