Fix IdleableHandlerThread.

Occasionally, ConnectivityServiceTest fails with "BUG: only one
idle handler allowed". I have not been able to reproduce this
consistently, but code inspection reveals an unsafe access to
mIdleHandler inside queueIdle. Wrap that in a synchronized block.

Change-Id: I27307e2e55fa8d937d7f043bd436894091c3c667

services/tests/servicestests/src/com/android/server/ConnectivityServiceTest.java

@@ -161,9 +161,11 @@ public class ConnectivityServiceTest extends AndroidTestCase {
                 assertNull("BUG: only one idle handler allowed", mIdleHandler);
                 mIdleHandler = new IdleHandler() {
                     public boolean queueIdle() {
-                        cv.open();
-                        mIdleHandler = null;
-                        return false;  // Remove the handler.
+                        synchronized (queue) {
+                            cv.open();
+                            mIdleHandler = null;
+                            return false;  // Remove the handler.
+                        }
                     }
                 };
                 queue.addIdleHandler(mIdleHandler);