To emphasize that the function requires `seastar::thread`
context to function properly.
Signed-off-by: Pavel Solodovnikov <pa.solodovnikov@scylladb.com>
This templates the code for listener_vector, renames it to
atomic_vector and moves it to the utils directory.
Signed-off-by: Rafael Ávila de Espíndola <espindola@scylladb.com>