build - Vagrant template to get more emulated PCI NICs

For some testing, it an be usefull to have more physical
NICS that DPDK's PMDs can bind to.
Example to run vpp within a VM with 3 emulated NICs:
  export VPP_VAGRANT_NICS=3
  vagrant up

Change-Id: I82d70f21c0a9ceba126ab6620c3b869d590d8de1
Signed-off-by: Vincent JARDIN <vincent.jardin@6wind.com>

build-root/vagrant/Vagrantfile

@@ -22,6 +22,15 @@ Vagrant.configure(2) do |config|
     config.cache.scope = :box
   end
 
+  # Define some physical ports for your VMs to be used by DPDK
+  nics = 0
+  if ENV.key?('VPP_VAGRANT_NICS')
+    nics = ENV['VPP_VAGRANT_NICS'].to_i(10)
+  end
+  for i in 1..nics
+    config.vm.network "private_network", type: "dhcp"
+  end
+
   # use http proxy if avaiable
   if ENV['http_proxy'] && Vagrant.has_plugin?("vagrant-proxyconf")
    config.proxy.http     = "$http_proxy"