Bug 1098168 - BaseIcon

Please update the icon also when NFC HW enabling/disabling is finished in ```NfcManager._handleNFCOnOff()```. You need to add the above line here [1] and removed the event dispatching code, since it's not used anymore after your changes. You'll need to update unit tests accordingly. Thank you.

[1] - https://github.com/alivedise/gaia/blob/bugzilla/1098168-rebase-master/statusbar-baseicon/apps/system/js/nfc_manager.js#L317