Don't let sign-in to network app appear in recents when it finishes

When the app exits there is no more work that can be accomplished
with it so don't let it be reactivated from the recents list.

Change-Id: I3dd67e033c5e68dac31e7a8c367eb81bd862dc21
Fixes: 29925057

packages/CaptivePortalLogin/src/com/android/captiveportallogin/CaptivePortalLoginActivity.java

@@ -96,7 +96,7 @@ public class CaptivePortalLoginActivity extends Activity {
         // Exit app if Network disappears.
         final NetworkCapabilities networkCapabilities = mCm.getNetworkCapabilities(mNetwork);
         if (networkCapabilities == null) {
-            finish();
+            finishAndRemoveTask();
             return;
         }
         mNetworkCallback = new NetworkCallback() {
@@ -163,7 +163,7 @@ public class CaptivePortalLoginActivity extends Activity {
                 mCaptivePortal.useNetwork();
                 break;
         }
-        finish();
+        finishAndRemoveTask();
     }
 
     @Override