providers/virtualbox: don't error when intnet set to "true" [GH-2751]

plugins/providers/virtualbox/action/network.rb

@@ -362,12 +362,15 @@ module VagrantPlugins
         end
 
         def intnet_adapter(config)
+          intnet_name = config[:intnet]
+          intnet_name = "intnet" if intnet_name == true
+
           return {
             :adapter => config[:adapter],
             :type => :intnet,
             :mac_address => config[:mac],
             :nic_type => config[:nic_type],
-            :intnet => config[:intnet]
+            :intnet => intnet_name,
           }
         end
 

test/acceptance/provider-virtualbox/network_intnet_spec.rb

@@ -0,0 +1,21 @@
+shared_examples "provider/network/intnet" do |provider, options|
+  if !options[:box]
+    raise ArgumentError,
+      "box option must be specified for provider: #{provider}"
+  end
+
+  include_context "acceptance"
+
+  before do
+    environment.skeleton("network_intnet")
+    assert_execute("vagrant", "box", "add", "box", options[:box])
+    assert_execute("vagrant", "up", "--provider=#{provider}")
+  end
+
+  after do
+    assert_execute("vagrant", "destroy", "--force", log: false)
+  end
+
+  it "properly configures an internal network" do
+  end
+end

test/acceptance/skeletons/network_intnet/Vagrantfile

@@ -0,0 +1,6 @@
+Vagrant.configure("2") do |config|
+  config.vm.box = "box"
+  config.vm.network "private_network",
+    ip: "192.168.50.4",
+    virtualbox__intnet: true
+end

vagrant-spec.config.example.rb

@@ -1,6 +1,9 @@
 require_relative "test/acceptance/base"
 
 Vagrant::Spec::Acceptance.configure do |c|
+  c.component_paths << File.expand_path("../test/acceptance", __FILE__)
+  c.skeleton_paths << File.expand_path("../test/acceptance/skeletons", __FILE__)
+
   c.provider "virtualbox",
     box: "<PATH TO MINIMAL BOX>",
     contexts: ["provider-context/virtualbox"]