Avoid runtime restart after vold reconnects.

Rely on behavior of already-released CountDownLatch instead of
clearing the reference.

Bug: 7290521
Change-Id: I787e673b97d18be412d5b37e279fbf1275b49151

Author: jsharkey

services/java/com/android/server/MountService.java

@@ -198,8 +198,8 @@ class VoldResponseCode {
     // Used as a lock for methods that register/unregister listeners.
     final private ArrayList<MountServiceBinderListener> mListeners =
             new ArrayList<MountServiceBinderListener>();
-    private CountDownLatch                        mConnectedSignal = new CountDownLatch(1);
-    private CountDownLatch                        mAsecsScanned = new CountDownLatch(1);
+    private final CountDownLatch mConnectedSignal = new CountDownLatch(1);
+    private final CountDownLatch mAsecsScanned = new CountDownLatch(1);
     private boolean                               mSendUmsConnectedOnBoot = false;
 
     /**
@@ -495,10 +495,6 @@ private void waitForReady() {
     }
 
     private void waitForLatch(CountDownLatch latch) {
-        if (latch == null) {
-            return;
-        }
-
         for (;;) {
             try {
                 if (latch.await(5000, TimeUnit.MILLISECONDS)) {
@@ -738,14 +734,12 @@ public void run() {
                  * the hounds!
                  */
                 mConnectedSignal.countDown();
-                mConnectedSignal = null;
 
                 // Let package manager load internal ASECs.
                 mPms.scanAvailableAsecs();
 
                 // Notify people waiting for ASECs to be scanned that it's done.
                 mAsecsScanned.countDown();
-                mAsecsScanned = null;
             }
         }.start();
     }