io_tester: bring back information about think time
io_tester: bring back information about think time

By accident, I ended up removing the think time setting from the class
description during last refactor. Bring it back.

Signed-off-by: Glauber Costa <7ba9037b0dd006f9408bd45b94707becd5cd4e87@scylladb.com>
Message-Id: <20180307001243.22358-1-7ba9037b0dd006f9408bd45b94707becd5cd4e87@scylladb.com>

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