Response from push server ignored

When Registrar#register is called, there is nothing that would check the server response, so even if the call wasn't successful, if it didn't throw an exception, it will be reported as a successful call.

On this line, HeaderAndBody object is being returned from the call but ignored and not verified:
https://github.com/aerogear/aerogear-android/blob/push/src/org/jboss/aerogear/android/unifiedpush/Registrar.java#L126