Disable some DtlsInStun testcases while merging new BoringSSL feature

We are on the brink of merging the new behavior of DTLSv1_set_initial_timeout_duration
which is awesome!
https://boringssl-review.googlesource.com/c/boringssl/+/86167

However, some of the testcases I written accidentally depends on the old
behavior. Therefor I need to disable some test until the boring ssl
change is merged, so I can re-enable the feature and update the tests
in the same change.

Sorry for mess :(

Bug: webrtc:367395350
Change-Id: I83605d60603b10af4517d7f40d62bc4d0758c378
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/442400
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Jonas Oreland <jonaso@webrtc.org>
Auto-Submit: Jonas Oreland <jonaso@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#46675}