Fix a misleading error log in ConnectTetheringOperation.

The existing message makes it sound like the wrong device responded with
a ConnectTetheringResponse, but really this log happens every time a
non-success response code is received.

Bug: None
Change-Id: I6c34857a30e86751febff93b13d84b3db6ddc883
Reviewed-on: https://chromium-review.googlesource.com/c/1450404
Commit-Queue: Jeremy Klein <jlklein@chromium.org>
Commit-Queue: Kyle Horimoto <khorimoto@chromium.org>
Auto-Submit: Jeremy Klein <jlklein@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#628431}

chromeos/components/tether/connect_tethering_operation.cc

@@ -148,7 +148,7 @@ void ConnectTetheringOperation::OnMessageReceived(
     }
   } else {
     PA_LOG(WARNING)
-        << "Received ConnectTetheringResponse from unexpected device with ID "
+        << "Received failing ConnectTetheringResponse from device with ID "
         << remote_device.GetTruncatedDeviceIdForLogs() << " and "
         << "response_code == " << response->response_code() << ".";
     error_code_to_return_ = ConnectTetheringResponseCodeToHostResponseErrorCode(