storage_proxy: Short circuit query without clustering ranges
storage_proxy: Short circuit query without clustering ranges

This patch makes the storage_proxy return an empty result when the
query doesn't define any clustering ranges (default or specific).

Signed-off-by: Duarte Nunes <a60e8b7496f7715d71354fe4c06dd24017025bf1@scylladb.com>

scylladb/scylla,scylladb/scylla,avikivity/scylla,duarten/scylla,duarten/scylla,avikivity/scylla,raphaelsc/scylla,raphaelsc/scylla,scylladb/scylla,scylladb/scylla,avikivity/scylla,duarten/scylla,raphaelsc/scylla