Add bidirectional (tradeoff) operation to iperf.

Increase unit test coverage.

BUG=chromium-os:23392
TEST=unit tests, cellular_Throughput

Change-Id: I740a538314def91262cd53fcdce844cfbd267bbc
Reviewed-on: https://gerrit.chromium.org/gerrit/12085
Reviewed-by: David Rochberg <rochberg@chromium.org>
Tested-by: David Rochberg <rochberg@chromium.org>
Commit-Ready: David Rochberg <rochberg@chromium.org>
2 files changed