Update usage of ActivityManagerNative.

- Remove references to ActivityManagerProxy.
- Add isSystemReady to ActivityManager.

Bug: 30977067
Test: cts/hostsidetests/services/activityandwindowmanager/util/run-test android.server.cts
      adb shell am instrument -e class com.android.server.am.ActivityManagerTest,com.android.server.am.TaskStackChangedListenerTest \
          -w com.android.frameworks.servicestests/android.support.test.runner.AndroidJUnitRunner
Change-Id: I07390b6124fb1515821f5c0b37baf6ae74adc8fa
diff --git a/services/core/java/com/android/server/LockSettingsShellCommand.java b/services/core/java/com/android/server/LockSettingsShellCommand.java
index 0efdd51..f72663a 100644
--- a/services/core/java/com/android/server/LockSettingsShellCommand.java
+++ b/services/core/java/com/android/server/LockSettingsShellCommand.java
@@ -20,7 +20,7 @@
 import static android.app.admin.DevicePolicyManager.PASSWORD_QUALITY_NUMERIC;
 import static com.android.internal.widget.LockPatternUtils.stringToPattern;
 
-import android.app.ActivityManagerNative;
+import android.app.ActivityManager;
 import android.content.Context;
 import android.os.Binder;
 import android.os.Process;
@@ -52,7 +52,7 @@
     @Override
     public int onCommand(String cmd) {
         try {
-            mCurrentUserId = ActivityManagerNative.getDefault().getCurrentUser().id;
+            mCurrentUserId = ActivityManager.getService().getCurrentUser().id;
 
             parseArgs();
             if (!checkCredential()) {