allow specification of mac in network command

lib/vagrant/action/vm/network.rb

@@ -65,6 +65,9 @@ module Vagrant
             adapter.enabled = true
             adapter.attachment_type = :host_only
             adapter.host_interface = network_name(network_options)
+            if network_options[:mac]
+              adapter.mac = network_options[:mac]
+            end
             adapter.save
           end
         end

lib/vagrant/config/vm.rb

@@ -55,6 +55,7 @@ module Vagrant
           :ip => ip,
           :netmask => "255.255.255.0",
           :adapter => 1,
+          :mac = nil,
           :name => nil
         }.merge(options || {})