Revert "Changed ConnectivityService#getServiceInstance so its a singleton."

This reverts commit 7323ea10cd which causes this exception:

E/SystemServer( 2653): Failure starting Connectivity Service
E/SystemServer( 2653): java.lang.IllegalMonitorStateException: object not locked by thread before wait()
E/SystemServer( 2653):  at java.lang.Object.wait(Native Method)
E/SystemServer( 2653):  at java.lang.Object.wait(Object.java:358)
E/SystemServer( 2653):  at com.android.server.ConnectivityService$ConnectivityThread.getServiceInstance(ConnectivityService.java:186)
E/SystemServer( 2653):  at com.android.server.ConnectivityService.getInstance(ConnectivityService.java:200)
E/SystemServer( 2653):  at com.android.server.ServerThread.run(SystemServer.java:262)

Change-Id: Idd139e426e61a1913b0bf343e2f0a0b1990ba8bb

services/java/com/android/server/ConnectivityService.java

@@ -105,7 +105,7 @@ public class ConnectivityService extends IConnectivityManager.Stub {
     private int mNumDnsEntries;
 
     private boolean mTestMode;
-    private static volatile ConnectivityService sServiceInstance;
+    private static ConnectivityService sServiceInstance;
 
     private Handler mHandler;
 
@@ -176,10 +176,11 @@ public class ConnectivityService extends IConnectivityManager.Stub {
             Looper.loop();
         }
 
-        public static synchronized ConnectivityService getServiceInstance(Context context) {
-            if (sServiceInstance == null) {
+        public static ConnectivityService getServiceInstance(Context context) {
             ConnectivityThread thread = new ConnectivityThread(context);
             thread.start();
+
+            synchronized (thread) {
                 while (sServiceInstance == null) {
                     try {
                         // Wait until sServiceInstance has been initialized.