Start virtualizationservice lazily

This CL fixes a bug that virtualizationservice is not started when
requested from an app. Use waitForService to do the lazy start.

Bug: 193593371
Test: run MicrodroiDemoApp
Change-Id: Ief17ef3c39e3e1ce926c6531bd7045fe3d4e4354
diff --git a/javalib/src/android/system/virtualmachine/VirtualMachine.java b/javalib/src/android/system/virtualmachine/VirtualMachine.java
index 7176486..3baec94 100644
--- a/javalib/src/android/system/virtualmachine/VirtualMachine.java
+++ b/javalib/src/android/system/virtualmachine/VirtualMachine.java
@@ -216,7 +216,8 @@
             throw new VirtualMachineException(this + " is not in stopped state");
         }
         IVirtualizationService service =
-                IVirtualizationService.Stub.asInterface(ServiceManager.getService(SERVICE_NAME));
+                IVirtualizationService.Stub.asInterface(
+                        ServiceManager.waitForService(SERVICE_NAME));
 
         try {
             if (mConsoleReader == null && mConsoleWriter == null) {