Captive portals: login activity probes like NetworkMonitor

This patch changes CaptivePortalLoginActivity captive portal test to be
consistent with NetworkMonitor by:
 - using Network.java to open the http connection.
 - adding a UserAgent property to the request header.

Test: manually tested.
Bug: 32369183

(cherry picked from commit 454e066e27a664e472152ba12f279ccfe0ec1225)

Change-Id: I559eb0497475daad758ba3b3395225dcd0a27a57
1 file changed
tree: f59f79e297323ce25b0c2e272b3b89a6cf89c081
  1. core/
  2. services/
  3. tests/