//test/cpp/end2end:xds_end2end_test is flaky on UBSAN #20695
Description
Saw failures in many recent builds on master.
https://source.cloud.google.com/results/invocations/e4cf8b14-1404-4fd2-a5fc-9d544f9decf3/targets
https://source.cloud.google.com/results/invocations/5831efb6-8e7f-43ca-b183-9ee7daf3c131/targets
The "Unevaluated target" might actually be a timeout problem.