Enable PARTIAL_CONNECTIVITY dialog

Enable PARTIAL_CONNECTIVITY dialog to complete the function.

Bug: 113450764
Test: 1. Build pass
      2. atest FrameworksNetTests
      3. atest NetworkStackTests
      4. Change captive_portal_https_url to https://invalid.com
      to simulate partial connectivity.

Change-Id: I5c9fe7a898d30d2f7f75142c85e73fefc257a147