range_streamer: Simplify multiple_map to map conversion in add_ranges
range_streamer: Simplify multiple_map to map conversion in add_ranges

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