Use magic geolocating Debian mirror

The previous mirror is quite slow, for people outside of China. This one should
auto-select a mirror that's geographically close to anyone using it.
Update to be compatible with current puppet

The current puppet-mysql module does not accept a config_hash parameter. Also,
use @ in templates to avoid deprecation warnings on more recent puppets.
Perform bootstrapping in Vagrant

Getting the system up shouldn't be any harder than "vagrant up". Configure
vagrant to run bootstrap.sh.