Fix TlsServerRevalidation flaky

The test becomes flaky because tls.clearQueries() is called without
tls.waitForQueries(). A recent change has made DnsTlsFrontend take
extra 50 ms to wait for another query from DoT validation, the test
will fail if tls.clearQueries() is called while DnsTlsFrontend is
still waiting for the query.

Original change: https://android-review.googlesource.com/c/platform/packages/modules/DnsResolver/+/1737639

Bug: 188153519
Bug: 191147599
Test: resolv_integration_test64 --gtest_filter="*TlsServerRevalidation"
      --gtest_repeat=100 --gtest_break_on_failure
Change-Id: Ieb81a407c2a9c6aa119ab4499a93a9ffd663b716
Merged-In: Ieb81a407c2a9c6aa119ab4499a93a9ffd663b716