API: add get_natural_endpoints to storage_service
API: add get_natural_endpoints to storage_service

This adds the get_natural_endpoints implementation to the
storage_service API.

Signed-off-by: Amnon Heiman <ed5fc74c4692051ad0b19749fd7cea6ec2d74b9e@scylladb.com>

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