(charmed-osm) Add auth to prometheus and update kafka/zk

- Authentication to prometheus:
  - Update prometheus relation to provide auth credentials (user/pass)
  - Update grafana datasource to include credentials to prometheus
- Update kafka and zookeeper charms:
  - Add support for the charms to talk to the new kafka charm
  - Add kafka and zookeeper charms in local bundle

Change-Id: Ifb83769583178f3a2069ae6756aa430ec69eecce
Signed-off-by: David Garcia <david.garcia@canonical.com>