Permit setting puppet tag during install
Currently, puppet either runs the whole catalog or nothing during the installation.
By adding a parameter, folks can curate a set of specific tags they'd like to run during the installation using tags they define. This will allow for people to select specific items they'd like to run using their own naming convention rather than defining `no_such_tag` as an actual tag that exists.
I've got exactly one class I'd like to run during the installation phase. Rather than attaching it to `no_such_tag` I can instead tell foreman to have puppet run the `installer_safe` tag.