Changed test to validate rtp timstamps not just in RTP packets but also in RTCP Sender Reports. Altered it to accept negative value since it is normal for RTCP packet coming before RTP packet to have slightly later time.
Changed test to validate rtp timstamps not just in RTP packets but also in RTCP Sender Reports.
Altered it to accept negative value since it is normal for RTCP packet coming before RTP packet to have slightly later time.

BUG=webrtc:5433

Review URL: https://codereview.webrtc.org/1633843003

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#11417}

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