core: Fix tests, which found broken logic in synced folders

lib/vagrant/action/builtin/synced_folders.rb

@@ -35,7 +35,11 @@ module Vagrant
             fs.each do |id, data|
               data[:hostpath] = File.expand_path(
                 data[:hostpath], env[:root_path])
-              data[:hostpath] = File.realpath(data[:hostpath])
+
+              # Expand the symlink if this is a path that exists
+              if File.file?(data[:hostpath])
+                data[:hostpath] = File.realpath(data[:hostpath])
+              end
 
               # Create the hostpath if it doesn't exist and we've been told to
               if !File.directory?(data[:hostpath]) && data[:create]

test/unit/vagrant/action/builtin/synced_folders_test.rb

@@ -4,6 +4,7 @@ require "tmpdir"
 require File.expand_path("../../../../base", __FILE__)
 
 describe Vagrant::Action::Builtin::SyncedFolders do
+  include_context "unit"
   include_context "synced folder actions"
 
   let(:app) { lambda { |env| } }