The initial dns seedlist discovery tests occasionally fail. This is likely due to a race between the SDAM machinery and the test assertions and SRV polling.

example failure: https://evergreen.mongodb.com/task_log_raw/mongo_rust_driver_tests__async_runtime~async_std_auth_and_tls~auth_and_tls_os~ubuntu_16.04_test_4.2_replica_set_68edbbf0d42b3241212ebbdf29cdfaff5987ea0e_20_09_24_20_47_35/0?type=T#L1301