test: Fix leak in io_queue_test
test: Fix leak in io_queue_test

The test allocates IO buffers for plain "new" call and doesn't
release them ever. The fix is in keeping the buffers in unique
ptrs and holding them until corresponding IO's future resolves.

tests: unit(debug)

Signed-off-by: Pavel Emelyanov <c9a32589e048e044184536f7ac71ef92fe82df3e@scylladb.com>
Message-Id: <20210405133710.9793-1-c9a32589e048e044184536f7ac71ef92fe82df3e@scylladb.com>

cloudius-systems/seastar,avikivity/seastar,avikivity/seastar,avikivity/seastar,syuu1228/seastar,cloudius-systems/seastar,scylladb/seastar,scylladb/seastar,scylladb/seastar,cloudius-systems/seastar,syuu1228/seastar,syuu1228/seastar