io_tester: Move class::name to public
io_tester: Move class::name to public

This method will be called from outside.

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

syuu1228/seastar,avikivity/seastar,cloudius-systems/seastar,avikivity/seastar,scylladb/seastar,cloudius-systems/seastar,avikivity/seastar,syuu1228/seastar,scylladb/seastar,syuu1228/seastar,cloudius-systems/seastar,scylladb/seastar