Prevent autostart after installation (Fix #86 Vagrant issue)

When provisioning on Vagrant for the first time, mongodb auto starts after installation. Because the virtual box by default has only 4GB storage, it will fail to run mongodb without specifying `nojournal` option. The second provision will be successful because it skips the install part and goes to `mongodb_instance` section where, if `nojournal` is specified in attribute, it knows to apply good configuration and start mongodb. fixes #86