Add option to skip and avoid captive portals.

Test: ConnectivityServiceTest updated with test cases.
Test: Manually tested against att-wifi in B42.
Bug: 30222699

(cherry picked from commit be96da11ccb5dd500f920c3ba90d350857293b3d)

Change-Id: I90c0f97fe0e41de4059bceae7b56ab3a70145696
4 files changed