Include and configure the restbase role on the test cluster

Also set up the cassandra seeds in hiera, so that the cassandra cluster nodes
can find each other & aren't as lonely any more.

Since this is for internal testing only we leave out passwords & encryption
for now. Default cassandra passwords will be used.

Change-Id: I330a3b8487b647f0d7c22b28d823a5b4f858dd59