PushClient tries to register also if Network is offline (failing...)

If network is offline, PushClient fails to get the push token (while this could be cached after the first run, I guess it's something somewhat expected).

The problem with that is in order to be able to retry to register the app on failures, we need to set the PushClient.appId to a non-empty value different than the previous one (using something like a " " string and back to old appID, to workaround this is not nice)...

So, in my opinion the PushClient should try to register only when NetworkingStatus.status == NetworkingStatus::Online, to avoid errors due do missing connection.
And in any case, the user should be able to retry the registration on failures, without using appId workarounds.

I've workarounded this by using a loader bound to NetworkingStatus.online (something such as http://pastebin.ubuntu.com/10580381/), but having something like this by default in the PushClient would be nice imho.