[Android] Stop emitting a nonzero value from the test runner if a device goes offline.

build/android/pylib/base/test_dispatcher.py

 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Dispatches tests, either sharding or replicating them.
 
 Performs the following steps:
 * Create a test collection factory, using the given tests
   - If sharding: test collection factory returns the same shared test collection
     to all test runners
@@ skipping 254 matching lines @@
   workers.StartAll()
 
   # Catch DeviceUnreachableErrors and set a warning exit code
   try:
     workers.JoinAll(watcher)
   except (device_errors.DeviceUnreachableError,
           # TODO(jbudorick) Remove this once the underlying implementations
           #                 for the above are switched or wrapped.
           android_commands.errors.DeviceUnresponsiveError) as e:
     logging.error(e)
-    exit_code = constants.WARNING_EXIT_CODE
 
   if not all((len(tc) == 0 for tc in test_collections)):
     logging.error('Only ran %d tests (all devices are likely offline).' %
                   len(results))
     for tc in test_collections:
       run_results.AddResults(base_test_result.BaseTestResult(
           t, base_test_result.ResultType.UNKNOWN) for t in tc.test_names())
 
   for r in results:
     run_results.AddTestRunResults(r)
@@ skipping 119 matching lines @@
   finally:
     try:
       _TearDownRunners(runners, setup_timeout)
     except (device_errors.DeviceUnreachableError,
             # TODO(jbudorick) Remove this once the underlying implementations
             #                 for the above are switched or wrapped.
             android_commands.errors.DeviceUnresponsiveError) as e:
       logging.warning('Device unresponsive during TearDown: [%s]', e)
     except Exception as e:
       logging.error('Unexpected exception caught during TearDown: %s' % str(e))