iotune: avoid "auto" parameters
iotune: avoid "auto" parameters

clang claims they are not valid C++.

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