change private network to public network

Signed-off-by: Dennis Rassmann <showp1984@gmail.com>

Vagrantfile

 Vagrant.configure(2) do |config|
 
   config.vm.box = "ubuntu/trusty64"
-  config.vm.network "private_network", ip: "10.1.1.11"
+  config.vm.network "public_network"
   config.vm.hostname = "dbserver"
 
   config.vm.provider "virtualbox" do |v|