CA-107031: IntelliCache cleanup script fails when VDI is not in XAPI database

Signed-off-by: Andrei Lifchits <andrei.lifchits@citrix.com>
Imported-by: Thanos Makatos <thanos.makatos@citrix.com>
Reviewed-by: Chandrika Srinivasan <chandrika.srinivasan@citrix.com>

GitHub: closes #124 on xapi-project/sm