storage_proxy: preserve endpoint's order while filtering local nodes for query
storage_proxy: preserve endpoint's order while filtering local nodes for query

filter_for_query() gets sorted by preference list of endpoints and
should preserve that order after filtering out non local endpoints for
local query. partition() does not guaranty this while stable_partition()
does, so use it instead.

Fixes #1450.
Message-Id: <9c4d7f0a6976c888a073b76b0211acd787481a49@scylladb.com>

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