Use networkType to display  wifi and mobile notification separately.

There are two bugs one is I was clearing the notification in
CaptivePortalTracker when entering the ActivateState. (double check
according to bug 5021626 we should be calling enter)

Second is we could have the need to display both icons but can't
because we only allow one.

The solution I'm proposing here is to allow two notifications and
have then controlled separately.

Bug: 10886908
Change-Id: I30e7130bc542535492d175640a4990c592f32806