gossiper: Coroutinize wait_for_gossip_to_settle()
gossiper: Coroutinize wait_for_gossip_to_settle()

Looks notably shorter this way

tests: unit(dev)

Signed-off-by: Pavel Emelyanov <c9a32589e048e044184536f7ac71ef92fe82df3e@scylladb.com>
Message-Id: <20220422093000.24407-1-c9a32589e048e044184536f7ac71ef92fe82df3e@scylladb.com>

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