This patch allows to pass custom parameters to the bootstrap-aio.yml
playbook by the `BOOTSTRAP_EXTRA_PARAMS` variable.
With `BOOTSTRAP_OPTS` it was only possible to set extra variables.
As an exmaple, `BOOTSTRAP_EXTRA_PARAMS` can be used to define custom
set of tags that should be executed.
Change-Id: Ie53b51f4e4d5ccbd0e7ff638a9d5bce236a561bd