test_runner.py Add --enable-concurrent-adb to --fast-mode

Missed this one first time around.

BUG=none

Review URL: https://codereview.chromium.org/1684193002

Cr-Commit-Position: refs/heads/master@{#374752}

build/android/test_runner.py

@@ -125,14 +125,15 @@ def AddCommonOptions(parser):
       namespace.verbose_count = max(namespace.verbose_count, 1)
       namespace.num_retries = 0
       namespace.enable_device_cache = True
+      namespace.enable_concurrent_adb = True
       namespace.skip_clear_data = True
       namespace.extract_test_list_from_filter = True
 
   group.add_argument('--fast-local-dev', type=bool, nargs=0,
                      action=FastLocalDevAction,
                      help='Alias for: --verbose --num-retries=0 '
-                          '--enable-device-cache --skip-clear-data '
-                          '--extract-test-list-from-filter')
+                          '--enable-device-cache --enable-concurrent-adb '
+                          '--skip-clear-data --extract-test-list-from-filter')
 
 def ProcessCommonOptions(args):
   """Processes and handles all common options."""