Basically, install the Debian packages (but nothing else) that a no-role instance uses, then export that as a MediaWiki-Vagrant box. Then, use that as the base box going forward.
This should make destroy/up much faster.
This could be re-done manually periodically (monthly?) initially. We could file a separate task to automate it later.
Idea how to do this:
1. In a new directory, make sure all roles are disabled.
2. vagrant up --provision.
3. dpkg --get-selections > packages.txt
4. Start a fresh VM using stock trusty-server-cloudimg-amd64-vagrant-disk1.box.
5. On that VM:
5a. sudo apt-get install dselect
5b. sudo dselect update
5c. sudo dpkg --set-selections < packages.txt
5d. sudo apt-get -y update
5e. sudo apt-get dselect-upgrade
6. Make sure right version of Guest Additions is installed.
7. vagrant package --base ubuntu-virtual-machine
See https://docs.vagrantup.com/v2/virtualbox/boxes.html .