Changes:
- Cluster entry is not removed from the table when a cluster is deleted because there are some foreign key constraints failing if the row delete is attempted. Instead the cluster is marked as 'removed'
- While deleting the pod changed the check to see if pod has any clusters - we now check that there are no clusters with removed column null.
- Also pod entry cannot be deleted from the db due to foreign key constraints. So added 'removed' column to Pod table host_pod_ref
- Now on deleting a pod, the pod will be marked as removed and pod name is set to null.