clustering_key_filter_ranges: Fix move assignment to avoid undefined behaviour.
clustering_key_filter_ranges: Fix move assignment to avoid undefined behaviour.

Get rid of the new(this) trick that results in undefined behaviour
because the class contains a const reference member.

Use std::reference_wrapper instead to ease the transition.

Refs #3032.

Signed-off-by: Vladimir Krivopalov <dc9186a06078733915a6fcbab34e59120be2b484@scylladb.com>
Message-Id: <5642bf79659231627dd7f8693c17cb46f274bcda.1533765105.git.dc9186a06078733915a6fcbab34e59120be2b484@scylladb.com>

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