Add test for internet availability on portals

Add a test verifying that when the device has detected a captive portal,
or when the user is trying to login to a captive portal, the captive
portal network does not become the default network if another network
can provide internet access.
This follows R CDD requirements.

Test: atest CtsNetTestCases:android.net.cts.CaptivePortalTest
Bug: 152280218
Change-Id: I6a97ed26dba665efdc67abb2371e0fc30ede020c
diff --git a/tests/cts/net/Android.bp b/tests/cts/net/Android.bp
index 76bb27e..46fae33 100644
--- a/tests/cts/net/Android.bp
+++ b/tests/cts/net/Android.bp
@@ -47,6 +47,7 @@
         "mockwebserver",
         "junit",
         "junit-params",
+        "libnanohttpd",
         "truth-prebuilt",
     ],