Revert "scylla_current_repo: support diffrent $PRODUCT"
Revert "scylla_current_repo: support diffrent $PRODUCT"

This reverts commit e5da79c211586ba49621858f3b1ac966153b6071 because the
URLs are incorrect: both open source and enterprise repository URLs are
in

  http://downloads.scylladb.com/rpm/centos/

or

  http://downloads.scylladb.com/deb/{debian,ubuntu}

scylladb/scylla,avikivity/scylla,avikivity/scylla,avikivity/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla