d775756d18
if the same vagrantfile is up'd in the same second in the same basedir this caused a conflict, most notably, all jenkins jobs sit in a 'workspace' directory, which breaks if more than one job launches from the same trigger.
Vagrant Core Plugins
These are plugins that ship with Vagrant. Vagrant core uses its own plugin system to power a lot of the core pieces that ship with Vagrant. Each plugin will have its own README which explains its specific role.