Allow boostrap with Buster

- add script and Vagrantfile code to preseed salt minion keys
- add needed bootstrap_options for Python 3 support
- add grains files and populate those of the ldap and web node
- add script to fix systemd-networkd setup with Debian libvirt Vagrant
  images
- switch from VirtualBox to libvirt

scripts/change-vmdebootstrap-default-dhcp.sh

@@ -0,0 +1,15 @@
+#!/bin/sh
+
+set -e
+
+debootstrap_network=/etc/systemd/network/99-dhcp.network
+
+if grep -q '^Name=\\*' "${debootstrap_network}"; then
+  primary_nic=$(ls -1 /sys/class/net | grep -v lo |sort | head -1)
+  sed -i "s/^Name=e\\*/Name=${primary_nic}/" \
+    "${debootstrap_network}"
+  systemctl restart systemd-networkd.service
+  echo "Changed systemd network configuration"
+else
+  echo "Systemd network configuration has already been changed"
+fi

scripts/pregen_keys.sh

@@ -0,0 +1,15 @@
+#!/bin/sh
+
+set -e
+
+if [ ! -d salt/keys ]; then
+    mkdir -p salt/keys
+fi
+ls -1 salt/grains | while read a; do
+    if [ ! -f salt/keys/$a.pem ]; then
+        openssl genrsa -out salt/keys/$a.pem 2048
+    fi
+    if [ ! -f salt/keys/$a.pub ]; then
+        openssl rsa -in salt/keys/$a.pem -pubout -out salt/keys/$a.pub
+    fi
+done