This is very likely the root cause of #20163 and #20695.

The current runtime of the test under TSAN is around ~2200 sec. That's not a reasonable test duration at all (it's bottle neck for our test latencies both on CI and when running tests manually) and as a side effect we're hitting some test infrastructure corner cases that are masking the underlying problem (e.g. #20695)

The evolution of the test duration (on TSAN, with other configurations there's a similar pattern):

• before 2019-10-17 the duration was ~750sec (already pretty high):
  https://source.cloud.google.com/results/invocations/d4e77a6c-a1d6-4523-98d8-a5f1d6cfdab0/targets;query=xds_end2end

• after merging Move XdsClient instantiation into xds resolver. #20476 it doubled to ~1500sec
  https://source.cloud.google.com/results/invocations/7144d3a9-c005-4154-b20b-a5ab9f9c3ad1/targets;query=xds_end2end_test

• then it further increased to ~2200sec (I wasn't able to track down the rootcause).
  https://source.cloud.google.com/results/invocations/ef0551a3-143f-4751-bc26-9fe41a1202d7/targets;query=xds_end2end