[8u60] Review request for RT-34840: [3DViewer] FileNotFoundException: Jfx3dViewerApp_session.properties (Read-only file system)

[Morris Meyer]

Kevin and Chien,

Please review this simple fix for the 3DViewer SessionManager class to 
take care of read-only file system errors when trying to save the 
session file.

Thanks much,

        --morris

JIRA - https://javafx-jira.kenai.com/browse/RT-34840
WEBREV - http://cr.openjdk.java.net/~morris/RT-34840.01