Remove notification right after clicking on cancel

After aosp/1188881, DynamicSystemManager.remove() is blocked for
about 30 seconds. To give users feedbacks faster when they click on
the [Cancel] button, This CL removes the progress notification
earlier.

Bug: 145891864
Test: Clicking on the [Cancel] button
Change-Id: I4e43775b2de6eaa50d4a1cc073a5057f22f6d8d5

packages/DynamicSystemInstallationService/src/com/android/dynsystem/DynamicSystemInstallationService.java

@@ -262,10 +262,11 @@ public class DynamicSystemInstallationService extends Service
             return;
         }
 
+        stopForeground(true);
         mJustCancelledByUser = true;
 
         if (mInstallTask.cancel(false)) {
-            // Will cleanup and post status in onResult()
+            // Will stopSelf() in onResult()
             Log.d(TAG, "Cancel request filed successfully");
         } else {
             Log.e(TAG, "Trying to cancel installation while it's already completed.");