systemvmtemplate: update debian 9.6 iso url and checksum (#3022)
systemvmtemplate: update debian 9.6 iso url and checksum (#3022)

This fixes the failing systemvmtemplate build due to 404 on old ISO url.

Signed-off-by: Rohit Yadav <902b9eb5dd62819678163bd5e00fbf0cbc7c264b@shapeblue.com>

GabrielBrascher/cloudstack,DaanHoogland/cloudstack,DaanHoogland/cloudstack,DaanHoogland/cloudstack,DaanHoogland/cloudstack,jcshen007/cloudstack,GabrielBrascher/cloudstack,DaanHoogland/cloudstack,jcshen007/cloudstack,jcshen007/cloudstack,jcshen007/cloudstack,GabrielBrascher/cloudstack,GabrielBrascher/cloudstack,DaanHoogland/cloudstack,GabrielBrascher/cloudstack,jcshen007/cloudstack,GabrielBrascher/cloudstack,DaanHoogland/cloudstack,GabrielBrascher/cloudstack,jcshen007/cloudstack,jcshen007/cloudstack