When fetching local devices for android tests, retry at most 4 times.

With four retries, that's a total of up to 30s of sleeping.

Bug: 892670
Change-Id: I59a870316bbd98e707907dfcb53c82a53a7beab9
Reviewed-on: https://chromium-review.googlesource.com/c/1291711Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: Ben Pastene <bpastene@chromium.org>
Cr-Commit-Position: refs/heads/master@{#601230}

build/android/pylib/local/device/local_device_environment.py

@@ -133,7 +133,8 @@ class LocalDeviceEnvironment(environment.Environment):
       device_arg = self._device_serials
 
     self._devices = device_utils.DeviceUtils.HealthyDevices(
-        self._blacklist, enable_device_files_cache=self._enable_device_cache,
+        self._blacklist, retries=4,
+        enable_device_files_cache=self._enable_device_cache,
         default_retries=self._max_tries - 1, device_arg=device_arg)
 
     if self._logcat_output_file: