Commit 7e3805ed3d removed the load balancing code from cql
server, but it did not remove most of the craft that load balancing
introduced. The most of the complexity (and probably the main reason the
code never worked properly) is around service::client_state class which
is copied before been passed to the request processor (because in the past
the processing could have happened on another shard) and then merged back
into the "master copy" because a request processing may have changed it.
This commit remove all this copying. The client_request is passed as a
reference all the way to the lowest layer that needs it and it copy
construction is removed to make sure nobody copies it by mistake.
tests: dev, default c-s load of 3 node cluster
Message-Id: <20190906083050.GA21796@scylladb.com>
f78b2c5588