packer: Add debian9 VM with bootstrap

packer/debian9-vm-bootstrap.json

+{
+    "variables": {
+        "user": "slapos",
+        "password": "slapos",
+        "disk_size": "200000",
+        "domain": ""
+    },
+
+    "builders":
+    [
+        {
+            "name": "debian9-vm-bootstrap",
+
+            "type": "qemu",
+            "format": "qcow2",
+            "accelerator": "kvm",
+            "disk_size": "{{ user `disk_size`}}",
+
+            "iso_url": "http://cdimage.debian.org/debian-cd/9.3.0/amd64/iso-cd/debian-9.3.0-amd64-netinst.iso",
+            "iso_checksum": "db8ab7871bc2b7d456c4746e706fb5d3",
+            "iso_checksum_type": "md5",
+
+            "http_directory": "http",
+
+            "ssh_username": "{{user `user`}}",
+            "ssh_password": "{{user `password`}}",
+            "ssh_wait_timeout": "1800s",
+            "shutdown_command": "echo '{{user `password`}}'|sudo -S shutdown -h now",
+
+            "headless": true,
+            "boot_wait": "2s",
+            "boot_command": [
+                   "<esc><wait><wait>",
+                   "install auto ",
+                   "preseed/url=http://{{ .HTTPIP }}:{{ .HTTPPort }}/preseed-debian9.cfg ",
+                   "debian-installer=en_US locale=en_US keymap=fr ",
+                   "netcfg/get_hostname={{ .Name }} ",
+                   "netcfg/get_domain={{ user `domain`}} ",
+
+                   "fb=false debconf/frontend=noninteractive ",
+
+                   "passwd/user-fullname={{user `user`}} ",
+                   "passwd/user-password={{user `password`}} ",
+                   "passwd/user-password-again={{user `password`}} ",
+                   "passwd/username={{user `user`}} ",
+
+                   "<enter>"
+            ]
+        }
+    ],
+
+    "provisioners": [
+        {
+            "type": "shell",
+            "execute_command": "echo '{{user `password`}}' | {{.Vars}} sudo -E -S bash '{{.Path}}'",
+            "scripts": [
+                "scripts/update.sh",
+                "scripts/packages.sh",
+                "scripts/cleanup.sh",
+                "scripts/vm-bootstrap.sh"
+            ]
+        }
+    ]
+}