map_difference: Define default value for key_comp
map_difference: Define default value for key_comp

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