contint: slave-scripts are deployed via git-deploy

The slave-scripts on CI production slaves (role::ci::slave) are deployed
via git-deploy (they have a deployment-target).

There is no more need to use  ontint::slave-scripts which was basically
using git::clone to fetch the scripts in /srv/slave-scripts.

Change-Id: Ida49e6ec11046e53d7a0fe088c555614d21b93d0