Update Vagrant#login_command to return a LoginCommand object.

This is the upstream API update needed to change directory before
issuing the SSH command to connect to a Test Kitchen controlled Vagrant
VM. Coolbeans.

lib/kitchen/driver/vagrant.rb

@@ -73,8 +73,7 @@ def destroy(state)
 
       def login_command(state)
         create_vagrantfile(state)
-        FileUtils.cd(vagrant_root, :verbose => logger.debug? ? true : false)
-        %W{vagrant ssh}
+        LoginCommand.new(%W{vagrant ssh}, :chdir => vagrant_root)
       end
 
       protected
@@ -85,9 +84,7 @@ def ssh(ssh_args, cmd)
 
       def run(cmd)
         cmd = "echo #{cmd}" if config[:dry_run]
-        FileUtils.cd(vagrant_root, :verbose => logger.debug? ? true : false) do
-          run_command(cmd)
-        end
+        run_command(cmd, :cwd => vagrant_root)
       end
 
       def vagrant_root