[unstable][asyncio] test_execute_query_timeout is unstable

[fruch]

since we enable asyncio tests in #260, this test is not stable under asyncio

FAILED tests/integration/standard/test_cluster.py::ClusterTests::test_execute_query_timeout - Exception: session.execute didn't time out in 10 tries

[fruch]

looks like the time in driver asyncio eventloop is using asyncio.sleep which doesn't work with timeout lower then 1ms.
try to see if the test can also work with 1ms as the lower timeout, and then adapt the test based on the event_loop

[fruch]

meanwhile I've decided to skip this test for asyncio

we might consider using https://gitlab.com/n23/atimer, to remove the limitation in general, but it's doesn't sound urgent to me...