Force host dns resolution for guest

Issue on osx 10.9.2 with virtualbox 4.3.8 where dns queries through certain programs like curl were timing out. Error was thrown in vagrant up for bootstrap.saltstack.org . 

Adding in config line from :https://leap.se/code/issues/1089 resolved the issue.
It was because of hm time and having to work with vagrant remotes... the incoming link didn't know where to go but changing the config fixed it. Didn't realise it would break other stuff. Sorry!