Fix (1) EndToEndTest.InitialProbing and (2) EndToEndTest.TriggerMidCallProbing
Fix (1) EndToEndTest.InitialProbing and (2) EndToEndTest.TriggerMidCallProbing

* EndToEndTest.InitialProbing had an uninitialized boolean.
* Both tests used RTC_DCHECK where one would normally expect an RTC_DCHECK.

BUG=webrtc:8085

Review-Url: https://codereview.webrtc.org/2998793002
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#19309}

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