service/client_state: don't allow modification of a system_trace KS
service/client_state: don't allow modification of a system_trace KS

Only users with enough permissions are allowed to modify system_trace KS.

Signed-off-by: Vlad Zolotarov <976c0f8d0852ed6439ad273880b400a75a7c41d0@cloudius-systems.com>

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