virgdbus: fix getting non-shared DBus connection

virgdbus: fix getting non-shared DBus connection

We need to pass some flags in order to properly initialize the
connection otherwise it will not work. This copies what GLib does
for g_bus_get_sync() internally.

This fixes an issue with LXC driver where libvirt was not able to
register any VM with machined.

Reported-by: Matthias Maier <tamiko@gentoo.org>
Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>