guests/ubuntu: enable the new mount_nfs stuff

plugins/guests/ubuntu/cap/mount_nfs.rb

@@ -1,4 +1,4 @@
-require_relative '../../linux/cap/mount_nfs'
+require Vagrant.source_root.join("plugins/guests/linux/cap/mount_nfs")
 
 module VagrantPlugins
   module GuestUbuntu
@@ -6,6 +6,7 @@ module VagrantPlugins
       class MountNFS < GuestLinux::Cap::MountNFS
         def self.mount_nfs_folder(machine, ip, folders)
           super
+
           # Emit an upstart events if upstart is available
           folders.each do |name, opts|
             real_guestpath =  machine.guest.capability(:shell_expand_guest_path, opts[:guestpath])

plugins/guests/ubuntu/cap/mount_virtualbox_shared_folder.rb

@@ -1,4 +1,4 @@
-require_relative '../../linux/cap/mount_virtualbox_shared_folder'
+require Vagrant.source_root.join("plugins/guests/linux/cap/mount_virtualbox_shared_folder")
 
 module VagrantPlugins
   module GuestUbuntu

plugins/guests/ubuntu/plugin.rb

@@ -16,16 +16,15 @@ module VagrantPlugins
         Cap::ChangeHostName
       end
 
+      guest_capability("ubuntu", "mount_nfs_folder") do
+        require_relative "cap/mount_nfs"
+        Cap::MountNFS
+      end
+
       guest_capability("ubuntu", "mount_virtualbox_shared_folder") do
         require_relative "cap/mount_virtualbox_shared_folder"
         Cap::MountVirtualBoxSharedFolder
       end
-
-      #I don't know if this works or not
-      #guest_capability("linux", "mount_nfs_folder") do
-      #  require_relative "cap/mount_nfs"
-      #  Cap::MountNFS
-      #end
     end
   end
 end