Update Vagrantfile.master_slave

vagrant up
Bringing machine 'node1' up with 'virtualbox' provider...
Bringing machine 'node2' up with 'virtualbox' provider...
Bringing machine 'node3' up with 'virtualbox' provider...
There are errors in the configuration of this machine. Please fix
the following errors and try again:

puppet provisioner:
* The following settings shouldn't exist: pp_path

To Fix this comment out #puppet.pp_path = "/tmp/vagrant-puppet"