Avoid DCHECK in P2PTransportChannel::MorePingable.
Avoid DCHECK in P2PTransportChannel::MorePingable.

Some implementations of std::max_element (used to find the "most
pingable" connection) seem to compare an element with itself, which
MorePingable doesn't handle.

Fixing by handling the self-comparison outside MorePingable.

Bug: webrtc:8697
Change-Id: Ieb34580f52037639c00041a4e65901cad92d0971
Reviewed-on: https://webrtc-review.googlesource.com/62402
Reviewed-by: Qingsi Wang <1c4f50fe02fab79f81be17f4e2f574c199f33efd@webrtc.org>
Commit-Queue: Taylor Brandstetter <f49cf6381e322b147053b74e4500af8533ac1e4c@webrtc.org>
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#22543}
ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc