This update for rubygem-vagrant-spec fixes the following issues:

* Run workflow on ubuntu image
* Update common.sh ci script
* Remove childprocess constraint
* Add a scenario for rebooting with provisioner
* Test: guest can write back to default synced folder
* Test synced folder persists after guest reboot
* Just load common.sh
* Use local vagrant gem if exists
* Update childprocess
* Add shebangs to scripts in acceptance/support-skeletons/triggers-advanced