This PR makes a few changes in the cstor-overview dashboard. The change include:
namespace variable changed to display namespaces where openebs is installed instead of having a drop-down to display all namespaces inside the cluster.
datasource was not be used by the individual panels. Changes are made so that this variable is used by the panels.
datasource value was hard-coded. Changed it and made it configurable via variables in grafana.
This PR makes a few changes in the cstor-overview dashboard. The change include: