Session cleanup in CSI driver

https://github.com/kubernetes-sigs/vsphere-csi-driver

improve VSphere session cleanup in the CSI driver code to improve session reuse and reduce lingering connections.

Start by reviewing the linked vSphere CSI driver repository and locating the session-handling code. Trace how sessions are created, reused, and cleaned up, then identify the expected behavior for lingering connections. Done means session reuse is improved and lingering connections are reduced, with validation in the relevant CSI driver tests if present.

Written by the indexing model from the issue text.