Currently --ami does not check instance types, creates invalid
io_properties.yaml on unsupported instance types.
It actually won't occur on AMI startup, since scylla_ami_setup only
invoke scylla_io_setup --ami when the instance is supported, so we don't
get the issue on startup, but we still get when we run scylla_io_setup
manually.
It's better to check instance type on scylla_io_setup, too.
Refs #5438
f21123b3ae