[Telemetry] Kill stray adb processes before gathering device list

telemetry/telemetry/internal/platform/android_device.py

Index: telemetry/telemetry/internal/platform/android_device.py
diff --git a/telemetry/telemetry/internal/platform/android_device.py b/telemetry/telemetry/internal/platform/android_device.py
index d99caedf82c151f9e930a325da9a1daa4a977939..f0eb82d361d1bd80fe319473e43811e1772da58e 100644
--- a/telemetry/telemetry/internal/platform/android_device.py
+++ b/telemetry/telemetry/internal/platform/android_device.py
@@ -4,6 +4,7 @@
 
 import logging
 import os
+import subprocess
 
 from telemetry.core import util
 from telemetry.internal.platform import cros_device
@@ -16,6 +17,11 @@ from devil.android import device_utils
 from devil.android.sdk import adb_wrapper
 
 
+def _KillStrayADBProcesses():
+  p = subprocess.Popen(['killall', 'adb'])
+  p.communicate()
+
+
 class AndroidDevice(device.Device):
   """ Class represents information for connecting to an android device.
 
@@ -34,6 +40,7 @@ class AndroidDevice(device.Device):
 
   @classmethod
   def GetAllConnectedDevices(cls, blacklist):
+    _KillStrayADBProcesses()
     device_serials = GetDeviceSerials(blacklist)
     return [cls(s) for s in device_serials]