test: ensure proper resource cleanup in integration tests (#537)

- Add try-finally blocks to guarantee server cleanup on test completion
- Call closeGracefully().block() to ensure synchronous shutdown
- Use try-with-resources for client lifecycle management where applicable
- Prevent resource leaks and potential test flakiness

Signed-off-by: Christian Tzolov <christian.tzolov@broadcom.com>

Author: tzolov