Don't bother enabling/configuring network adapters if there are none

lib/vagrant/action/vm/network.rb

@@ -41,6 +41,7 @@ module Vagrant
             networks << network
           end
 
+          if !adapters.empty?
             # Automatically assign an adapter number to any adapters
             # that aren't explicitly set.
             @logger.debug("Assigning adapter locations...")
@@ -53,11 +54,13 @@ module Vagrant
             @logger.info("Enabling adapters...")
             env[:ui].info I18n.t("vagrant.actions.vm.network.preparing")
             env[:vm].driver.enable_adapters(adapters)
+          end
 
           # Continue the middleware chain. We're done with our VM
           # setup until after it is booted.
           @app.call(env)
 
+          if !adapters.empty?
             # Determine the interface numbers for the guest.
             assign_interface_numbers(networks, adapters)
 
@@ -65,6 +68,7 @@ module Vagrant
             env[:ui].info I18n.t("vagrant.actions.vm.network.configuring")
             env[:vm].guest.configure_networks(networks)
           end
+        end
 
         # This method assigns the adapter to use for the adapter.
         # e.g. it says that the first adapter is actually on the