Fix disconnectFrom{Peer,Bus} when the connection failed

If the connection failed, the DBusConnection object is null, but we
still add our QDBusConnectionPrivate to the global hash (maybe we
shouldn't). Both disconnectFromXXX functions check that they are
disconnecting a connection of the right type, but we never initialized
the type if the connection failed.

So simply make sure we initialize before handling the error state.

Task-number: QTBUG-27973
Change-Id: I96f4825ab1b71adf1b72caf4f72db41742b44a55
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@digia.com>
QCoreApplication: Removed out-of-date docs (argv() method).

QCoreApplication::argv() method was obsolete in Qt4.8
and removed in Qt5.0.

Change-Id: I217402f774f5509c8ca317a35c831ffa5ac2af06
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>