GitLab

Since we no longer need to juggle TURN and GTURN ICE configs, we can
remove the relay_mode_ member and code needed for it.  This simplifies
things a bit in preparation for the removal of the ICE Config caching
logic.

Change-Id: Ibcc34368c6f3df943cbcb6b1365bc87d30af2dec
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2187201Reviewed-by: Yuwei Huang <yuweih@chromium.org>
Commit-Queue: Joe Downing <joedow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#766526}