Send BUGREPORT_REQUESTED broadcast to system user

This broadcast should have a qualified user since
it is being sent from the system. This broadcast
is being sent to the shell, so we should use
UserHandle.SYSTEM.

Test: atest CtsBugreportTestCases, check logcat
      for warnings
Bug: 180769102
Change-Id: I3bebc886cf9931ea79fa0e91312d8720e5bd0e7d

services/core/java/com/android/server/am/ActivityManagerService.java

@@ -6487,7 +6487,7 @@ public class ActivityManagerService extends IActivityManager.Stub
         final long identity = Binder.clearCallingIdentity();
         try {
             // Send broadcast to shell to trigger bugreport using Bugreport API
-            mContext.sendBroadcast(triggerShellBugreport);
+            mContext.sendBroadcastAsUser(triggerShellBugreport, UserHandle.SYSTEM);
         } finally {
             Binder.restoreCallingIdentity(identity);
         }