utils/flush_queue: Add ability to wait with a timeout
utils/flush_queue: Add ability to wait with a timeout

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