Explicitly set the HttpURLConnection methods to deflake tests

Explicitly set the HttpURLConnection methods so that these will
not interact with real methods to prevent threading issue in
the test.

Fix: 296168371
Test: atest NetworkMonitorTest --iteractions 50 on cuttlefish
Change-Id: Id6e0a9f973d65fe1c211ce07743ff62e3816854c
1 file changed