[Sb refactor] [demo] Use better default for demo mode

DemoModeConnectionsRepository was using (isConnected = false, isValidated
= false) for its default mobile connectivity model, and doesn't yet
support updating those values via the command line.

This CL just changes the default to be (true, true) so that the icons
properly show up.

Test: manual demo mode
Bug: 238425913
Change-Id: I1c9ade7ed0bd3c278ed38a3b306627a2879fb83e