system_keyspace: Remove local host id from local cache
system_keyspace: Remove local host id from local cache

This value is now write-only, all readers had been patched
to use db::config copy

Signed-off-by: Pavel Emelyanov <c9a32589e048e044184536f7ac71ef92fe82df3e@scylladb.com>

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla