Refs #1826: CyNetworks and CyNetworkViews loaded from a cancelled Open Session Task are now disposed.

Change-Id: I8c84ab1bda84519687dc430d66461c0a49a1a03e
Fixes #1826: Open Session tasks also dispose CyNetworkViews/CyNetworks when the user cancels the new loaded session after the Session Reader is finished.

Change-Id: I8ae1020f1b657e658af769797645dadf89068f8e