fix typo in Vagrantfile

Enjoyed your blog entry http://dougmcclure.net/blog/2013/03/from-zero-to-search-in-15-minutes-using-vagrant-to-explore-ibm-log-analytics/
Started going though it. Vagrant threw an error due to minor typo.
Note. The original line is also in the blog so if the proposed fix is accepted you might wish to update that line as well.