Fix bugs and improve monitoring support.

Fixed test setup issue and missing cleanup of monitoring firewall rules.
Added logic to generate an unique password for Grafana as part of Cluster bring up
Modified the pod description to always use the 'latest' image to avoid pulling all the tags, thereby reduce startup latency.
cc @lavalamp 
Use [[ ... ]] and quote the arguments:

```shell
  if [[ "${MONITORING}" == "true" ]]; then
    ...
```