New system property "sys.boot_completed" set to 1 when boot completed.

Change-Id: Ie3fc0b1efdfb637b0c780064a71e8c1575e15ca3
diff --git a/services/java/com/android/server/am/ActivityManagerService.java b/services/java/com/android/server/am/ActivityManagerService.java
index 162fffe..dff6a8a 100644
--- a/services/java/com/android/server/am/ActivityManagerService.java
+++ b/services/java/com/android/server/am/ActivityManagerService.java
@@ -3571,6 +3571,7 @@
             
             if (mFactoryTest != SystemServer.FACTORY_TEST_LOW_LEVEL) {
                 // Tell anyone interested that we are done booting!
+                SystemProperties.set("sys.boot_completed", "1");
                 broadcastIntentLocked(null, null,
                         new Intent(Intent.ACTION_BOOT_COMPLETED, null),
                         null, null, 0, null, null,