VMDK: bugfix, opening vSphere 4 exported image The vSphere 4 exported image is streamOptimized extent, which is not quite correctly handled. Ignore rdgOffset when RGD flag bit not set. Signed-off-by: Fam Zheng <famcool@gmail.com> Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>