Make the windows test only run on windows for now until it can pass on unix

test/vagrant/env_test.rb

@@ -246,10 +246,14 @@ class EnvTest < Test::Unit::TestCase
     end
 
     should "return false if not found on windows-style root" do
+      # TODO: Is there _any_ way to test this on unix machines? The
+      # expand path doesn't work [properly for the test] on unix machines.
+      if RUBY_PLATFORM.downcase.include?("mswin")
         # Note the escaped back slash
         path = Pathname.new("C:\\")
         assert !Vagrant::Env.load_root_path!(path)
       end
+    end
 
     should "should set the path for the rootfile" do
       path = "/foo"