Collect watchdog stacks from vold.

We're seeing evidence that vold is getting wedged.

Bug: 122090837
Test: manual
Change-Id: I1791ee62ebfad5705c4ecdbf6c6c6b2f20267fb4
diff --git a/services/core/java/com/android/server/Watchdog.java b/services/core/java/com/android/server/Watchdog.java
index e80e9e1..1aeb689 100644
--- a/services/core/java/com/android/server/Watchdog.java
+++ b/services/core/java/com/android/server/Watchdog.java
@@ -91,6 +91,7 @@
         "/system/bin/mediaserver",
         "/system/bin/sdcard",
         "/system/bin/surfaceflinger",
+        "/system/bin/vold",
         "media.extractor", // system/bin/mediaextractor
         "media.metrics", // system/bin/mediametrics
         "media.codec", // vendor/bin/hw/android.hardware.media.omx@1.0-service