tempest-smoke.sh -> install-devstack-xen.sh

tempest-smoke.sh is the script that was ran by the CI system. This
change removes the old install-devstack-xen.sh script, and replaces that
by tempest-smoke.sh. This way people will run the same script that is
running in the CI.
Get rid of old ci scripts

This change removes the old scripts, that are no longer used.