Fix updating degradation preference in SetRtpParameters.
Fix updating degradation preference in SetRtpParameters.

Degradation preference could be changed before video send stream
is configured which would cause a crash.

Bug: None
Change-Id: If970e66fba0b9fdb9da789066861d919874de119
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/164463
Reviewed-by: Niels Moller <0057859e47d61d90529d0f66d9ef692cefedb46a@webrtc.org>
Commit-Queue: Mirta Dvornicic <c6f473f74a061e7a4ef17c2c04eac029911f2b6c@webrtc.org>
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#30141}

ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc