Fix WifiTile's Connected indicator for ephemeral networks.

Such networks do not have a WifiConfiguration and need to be matched
by SSID.

Note a subtle difference with platform settings: in platform settings,
selecting an ephemeral network saves it for future use. That feels out
of place here, where normally clicking on the connected network does
nothing.

Bug: 18489098
Change-Id: I6aebd14054af47f078ffd8d754668817dff90436