Fix memory leaks of OpenKVRepo objects (leads to crash with PostgreSQLException when exceeds limit of DB connections)

Type of change

• Bug Fix
• Feature

Does this introduce a change in the core logic?

• [No]

Does this introduce a change in the cloud provider implementation, if so which cloud?

• AWS
• Azure
• GCP
• IBM

Updates description?

Fixes issue #44 (closed) (crash with PostgreSQLException).

The reason is memory leaks of OpenKVRepo objects, which leads to crash with PostgreSQLException when exceeds limit of DB connections.