dist/common/scripts/scylla_setup: don't accept disk path if it's not block device
dist/common/scripts/scylla_setup: don't accept disk path if it's not block device

Need to ignore input when specified path is not block device.

scylladb/scylla,scylladb/scylla,duarten/scylla,avikivity/scylla,scylladb/scylla,duarten/scylla,avikivity/scylla,duarten/scylla,avikivity/scylla,scylladb/scylla