Fixing P2PTransportChannelTest.TestIceConfigWillPassDownToPort.
Fixing P2PTransportChannelTest.TestIceConfigWillPassDownToPort.

Was flaky because it was checking the role of a port, but a role
conflict could occur before this happened which would swap the
role.

BUG=webrtc:6019
R=honghaiz@webrtc.org, pthatcher@webrtc.org
TBR=honghaiz@webrtc.org

Review URL: https://codereview.webrtc.org/2108493003 .

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#13327}

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