[packagekit] backend initialized multiple times when using pk-application

[Andreas]

> I've added some code to PackageKit daemon to detect for this sort of
> init failure, and hopefully handle it in a sane way. Does code from the
> tonight's internal git server work better?
> 
Yes, the whole thing works again. I still get a warning from glib
because of a non PkBackend type pointer though. And there's always 1 job
in progress so the daemon never idles. Perhaps I just forgot to emit
finished somewhere...
Thanks for the fix.

Andreas