Migrate Java GUI/CLI added clusters into WebUI

Credential management for JAVA GUI/CLI and WebUI are separate.

Clusters added via Java GUI/CLI won't be reflected in WebUI and vice-e-versa.
If there are any existing clusters in Java GUI/ CLI, user must manually add these cluster/clusters and its credentials in WebUI.
Note:
Once a cluster is added in WebUI and then if it is deleted from Java GUI/CLI, the cluster would still exist in WebUI and vice-versa.
Once the cluster is added in WebUI and if the cluster credential needs to be updated, it must be updated from WebUI only.
Consider the following scenario:
- A cluster exists in both WebUI and Java UI.
- Cluster credential is updated in WebUI only.
- The cluster is deleted from WebUI.
Impact: Backups and restores may fail on Java GUI as the credential of cluster added in Java GUI was not updated.
Recommendation:Update the credential from Java GUI.
After the cluster is added in WebUI, the backups with existing policies would still be successful, even if the cluster is deleted from Java GUI. However, restore jobs can not be triggered from Java GUI in this scenario; as it requires cluster to be present on Java GUI.
If a cluster is added from Java GUI and WebUI and then it is deleted it from Java GUI, the cluster can still be seen at WebUI and vice-versa.
If a cluster was in WebUI as well as Java GUI and its credential was updated in WebUI and then the cluster is deleted from WebUI, backup and restores may fail as the cluster added in Java UI was not updated. One may have to update the credential from Java UI to get things working.