commitlog::read_log_file: Don't discard a future
commitlog::read_log_file: Don't discard a future

This makes the code a bit easier to read as there are no discarded
futures and no references to having to keep a subscription alive,
which we don't with current seastar.

Signed-off-by: Rafael Ávila de Espíndola <espindola@scylladb.com>

Message-Id: <4c3f0a2552c9cc13159785bea893d312e08e2f83@scylladb.com>

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