Make network_WiFi_VerifyRouter give meaningful failure information

Now when this test fails, it throws an error like:

Failed to connect when (bitmap=2, ap_instance=1, channel=6),
  (bitmap=2, ap_instance=1, channel=136).

which is helpful in diagnosing problems.

Note that we now try all possible combinations of antennas before
failing.

BUG=None
TEST=This test passes updated routers, and fails with messages like
above appropriately.

Change-Id: I94eab6a83fa870f34c2eeae60edb5b4267d34079
Reviewed-on: https://chromium-review.googlesource.com/189696
Tested-by: Christopher Wiley <wiley@chromium.org>
Reviewed-by: Paul Stewart <pstew@chromium.org>
Commit-Queue: Christopher Wiley <wiley@chromium.org>
1 file changed