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 <[email protected]>

Author: yadvr

tools/appliance/systemvmtemplate/template.json

@@ -38,8 +38,8 @@
       "disk_interface": "virtio",
       "net_device": "virtio-net",
 
-      "iso_url": "https://cdimage.debian.org/debian-cd/current/amd64/iso-cd/debian-9.5.0-amd64-netinst.iso",
-      "iso_checksum": "efe75000c066506326c74a97257163b3050d656a5be8708a6826b0f810208d0a58f413c446de09919c580de8fac6d0a47774534725dd9fdd00c94859e370f373",
+      "iso_url": "https://cdimage.debian.org/debian-cd/current/amd64/iso-cd/debian-9.6.0-amd64-netinst.iso",
+      "iso_checksum": "fcd77acbd46f33e0a266faf284acc1179ab0a3719e4b8abebac555307aa978aa242d7052c8d41e1a5fc6d1b30bc6ca6d62269e71526b71c9d5199b13339f0e25",
       "iso_checksum_type": "sha512",
 
       "vm_name": "systemvmtemplate",