Try to deflake VideoSendStream tests with ULPFEC.
Try to deflake VideoSendStream tests with ULPFEC.

The changes here are the same as in https://codereview.webrtc.org/2523993002/:
- reduce packet loss from 50% to 5%, to allow the BWE to ramp up better.
- Do not wait for 100 packets to be sent before letting the test pass.

BUG=webrtc:6851

Review-Url: https://codereview.webrtc.org/2558303002
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#15542}

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