bug 446117: Default Session Timeout for ajaxSessionCache too small

https://bugs.eclipse.org/bugs/show_bug.cgi?id=446117

Change-Id: I1acd8f26ca8650f44a01d45b4dc32259ffa70609
Signed-off-by: Judith Gull <jgu@bsiag.com>
Reviewed-on: https://git.eclipse.org/r/34554
Tested-by: Hudson CI