Store and pull files from /sdcard/

Tradefed FilePullerLogCollector can no longer access the internal app directory (e.g. /storage/emulated/0/Android/data/com.android.server.wm.flicker/files).

This makes it unable to pull trace files, when a test fails. This CL makes flicker tests store their data on /sdcard/flicker which can be accessed by the Tradefed FilePullerLogCollector

Bug: 171026227
Test: atest FlickerTests
Change-Id: Ibed6b621b068b0668d93b39838c0959441527295
diff --git a/tests/FlickerTests/AndroidTestPhysicalDevices.xml b/tests/FlickerTests/AndroidTestPhysicalDevices.xml
index 1650438..abd620f 100644
--- a/tests/FlickerTests/AndroidTestPhysicalDevices.xml
+++ b/tests/FlickerTests/AndroidTestPhysicalDevices.xml
@@ -34,7 +34,7 @@
         <option name="hidden-api-checks" value="false" />
     </test>
     <metrics_collector class="com.android.tradefed.device.metric.FilePullerLogCollector">
-        <option name="directory-keys" value="/storage/emulated/0/Android/data/com.android.server.wm.flicker/files" />
+        <option name="directory-keys" value="/sdcard/flicker" />
         <option name="collect-on-run-ended-only" value="true" />
         <option name="clean-up" value="true" />
     </metrics_collector>