Fix Vagrant 1.2.x warnings

the current created Vagrantfile is for Version 1 (see #2523 (closed)).

Vagrant 1.2.x uses the config version 2, and will warn about deprecated options:

--- git/bitmask ‹develop› » leap local start web1
There were warnings and/or errors while loading your Vagrantfile.
Your Vagrantfile was written for an earlier version of Vagrant,
and while Vagrant does the best it can to remain backwards
compatible, there are some cases where things have changed
significantly enough to warrant a message. These messages are
shown below.

Warnings:
* `config.vm.customize` calls are VirtualBox-specific. If you're
using any other provider, you'll have to use config.vm.provider in a
v2 configuration block.

Bringing machine 'web1' up with 'virtualbox' provider...
[web1] Setting the name of the VM...
[web1] Clearing any previously set forwarded ports...
[web1] Creating shared folders metadata...
[web1] Clearing any previously set network interfaces...
[web1] Preparing network interfaces based on configuration...
[web1] Forwarding ports...
[web1] -- 22 => 2222 (adapter 1)
[web1] Running any VM customizations...
[web1] Booting VM...
[web1] Waiting for VM to boot. This can take a few minutes.
[web1] VM booted and ready for use!
[web1] Configuring and enabling network interfaces...
[web1] Mounting shared folders...
[web1] -- /vagrant
[web1] -- /srv/varac-dev
There were warnings and/or errors while loading your Vagrantfile.
Your Vagrantfile was written for an earlier version of Vagrant,
and while Vagrant does the best it can to remain backwards
compatible, there are some cases where things have changed
significantly enough to warrant a message. These messages are
shown below.

Warnings:
* `config.vm.customize` calls are VirtualBox-specific. If you're
using any other provider, you'll have to use config.vm.provider in a
v2 configuration block.

[web1] Already sandbox mode

(from redmine: created on 2013-07-23, closed on 2013-07-26, relates #2496 (closed))