Add flags to control Disk_Size & unattended-up

During internal use of PICO for teaching purposes, two
issues often popped up:
1. Something kept breaking down (auth for example), due to
background updates
2. Students often used vs-code servers, which in a class of 90,
ate up the 10GB default disk space

These changes implement:
- "DISK_SIZE": An environment variable with value of the form
`XGB` with X being a numberic value, to control max disk size.
- "disable-unattended-upgrades": A Flag in the anisble config to
uninstall `unattended-upgrades`, preventing unwanted updates on
private deployments.

Vagrantfile

@@ -6,6 +6,8 @@
 
 require 'etc'
 
+ENV['VAGRANT_EXPERIMENTAL'] = "disks"
+
 # Extract suffix if working directory starts with prefix; otherwise return "".
 def compute_auto_name_suffix(prefix = "picoCTF")
   dirname = File.basename(Dir.getwd)
@@ -16,6 +18,7 @@ Vagrant.configure("2") do |config|
 
   config.vm.define "shell", primary: true do |shell|
     shell.vm.box = "ubuntu/bionic64"
+    shell.vm.disk :disk, size: (ENV['DISK_SIZE'] || "10GB"), primary: true
     shell.vm.network "private_network", ip: (ENV['SIP'] || '192.168.2.3'), nic_type: "virtio"
     shell.vm.network "forwarded_port", guest: 2376, host: 2223, auto_correct: true
 

ansible/common/tasks/utils.yml

@@ -20,3 +20,10 @@
         ]
   environment:
     DEBIAN_FRONTEND: noninteractive
+
+- name: Disable unattended upgrades
+  apt:
+    state: absent
+    name: unattended-upgrades
+    purge: True
+  when: disable_unattended_upgrades | default(false) | bool

infra_local/inventory.yml

@@ -20,6 +20,8 @@ all:
   vars:
       # SSH admin keys (Optional)
       admin_keys                  : []
+      # Disable Unattended Upgrades
+      disable_unattended_upgrades : False
 
       # Web automation and Features (Optional)
       auto_add_web_admin          : True

infra_remote/inventory.yml

@@ -47,6 +47,8 @@ all:
 
       # SSH admin keys (Optional)
       admin_keys : []
+      # Disable Unattended Upgrades
+      disable_unattended_upgrades : False
 
       ## Web automation and Features (Optional):
       # These are currently setup to fully configure and start an event. This