scylla_setup: skip iotune when developer_mode is enabled
scylla_setup: skip iotune when developer_mode is enabled

When developer mode automatically enabled on nonroot mode, we should skip
iotune since the parameter won't be used.

Closes #7327

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