The client::session::test::cluster_time_in_commands test fails every now and then. We should investigate the cause of the failures and fix them.

example failure: https://evergreen.mongodb.com/task_log_raw/mongo_rust_driver_tests__async_runtime~tokio_auth_and_tls~noauth_and_notls_os~ubuntu_16.04_test_4.4_sharded_cluster_patch_3569cc2279c8a357f0bc332df4b8f990acf61939_60ae94bfc9ec444e290e5296_21_05_26_18_34_40/0?type=T