provision-vagrant: A few changes to support other container systems.
This is preliminary work to remove some Vagrant assumptions, to enable using the same provisioning script with other container/virtualization systems (particularly to add support for LXC).
- Renamed support/provision-vagrant to provision-test-environment to remove the assumption that it only works with vagrant. Vagrantfile was updated accordingly. - Short explanation of how the script runs - Made CHECKBOX_TOP relocatable to the parameter the script receives, though we default to /vagrant if we didn't receive anything else. This is because test-in-lxc can place the source tree in an unpredictable location and provision needs to be aware of the location. - Made the Vagrant sanity check conditional on $CHECKBOX_TOP being /vagrant. - Modified the code to create the $HOME/src symlink to account for different container/VM engines since lxc behavior is different from Vagrant, this is explained in the comment for the last section of the script.