Use mContext directly, and enforce via logging

We already have the context saved, so we can just use that.
Add a log statement so we can test for the existence of this patch from
a CTS test.

Test: Edited code to force expection path to be called, confirmed
      reboot happens
Bug: 138952436
Bug: 140111727

Change-Id: Iaceec82d4716837158d1233400b4a44cbf67a5e8

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

@@ -5255,6 +5255,9 @@ public class ActivityManagerService extends IActivityManager.Stub
 
         // Inform checkpointing systems of success
         try {
+            // This line is needed to CTS test for the correct exception handling
+            // See b/138952436#comment36 for context
+            Slog.i(TAG, "About to commit checkpoint");
             IStorageManager storageManager = PackageHelper.getStorageManager();
             storageManager.commitChanges();
         } catch (Exception e) {