[rilmodem] Re-work ril plugin's atom creation/destruction logic

[Tony Espy]

Device: mako
Channel, Image: ubuntu-rtm/14.09-proposed, #135

While working on test scripts for the SIM sub-section of the ofono test plan verification of the modem's "Interfaces" I ran into a couple of odd problems caused by the rilmodem device plugin ( ril ).

First, on a mako with no SIM, when the modem is set offline, the RadioSettings interface doesn't get destroyed. If the device boots in offline state, RadioSettings is not available.

Second, there are many interfaces available when the modem is offline that probably shouldn't be. These include:

ConnectionManager
CallForwarding
SmartMessaging
PushNotification** ( this might make sense due to it's registration mechanism )
MessageManager
NetworkTime
MessageWaiting