dist/common/scripts/scylla_setup: use specified NIC ifname correctly
dist/common/scripts/scylla_setup: use specified NIC ifname correctly

Interactive NIC selection prompt always returns 'eth0' as selected NIC name
mistakenly, need to fix.

Fixes #3651

Signed-off-by: Takuya ASADA <4ebfb6f510af412d6e89fefa3ab96d9c8b5e3fff@scylladb.com>
Message-Id: <20180803020724.15155-1-4ebfb6f510af412d6e89fefa3ab96d9c8b5e3fff@scylladb.com>

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