Eliminate blocking D-Bus calls in QOfonoManager

QOfonoManager constructor was actually making two blocking calls - first org.ofono.Manager.GetModems and then org.ofono.Modem.GetProperties (per each modem but we only have one). The latter was totally unnecessary because GetModems returns all the modem properties, there's no need to query them again.
Well, I can't think of any useful error messages here. Here's why:

1. The only plausable reasons for a failure are catastrophic D-Bus or ofono failures. That won't go unnoticed without any additional error messages from libqofono.
2. Since this is a shared library, any error message caused by an external condition (such as the death of ofono or dbus-daemon) can potentially get muiltiplied by the number of processes that have this library loaded. Since it's not really necessary (see the item number 1) I would rather avoid littering the journal with multiple copies of useless error messages.

Regarding error handling, ofono death will result in ofonoUnregistered slot getting invoked, where everything is cleaned up. Once ofono gets restarted, connectToOfono is called again and hopefully things work better next time around. And dbus-daemon failure is probably unrecoverable.