Fix Slow Vagrant DNS

This does a bit more than just fix the networking issue. Trying to keep it localized to that single issue is challenging because of how long Vagrant can take to run. This is a long overdue update to the Vagrantfile and reduces the time of `vagrant up; vagrant ssh; make bootstrap` from ~30min to ~6m.

* Changes networking before puppet runs to use `single-request-reopen`. 
* Changes mount point from `src/socorro` to just `socorro`
* Defaults the Vagrant config to version 2.
* Removes use of `vagrantconfig*.yaml`
* Removes debugging options that relied on vagrantconfig
* Removes symlink settings that come default in Vagrant >= 4.