[packagekit] Cancel method for dbus backends

[Robin Norwood]

Hi,

I added a Cancel method for the yum2 backend, but it still doesn't
work.  Reading the dbus and dbus-python docs, AFAICT we're doing
everything correctly to allow an asych call, but the Cancel call still
isn't executed until after whatever action we're trying to cancel is
over.  Any idea what I'm doing wrong here?

Thanks,

-RN

-- 
Robin Norwood
Red Hat, Inc.

"The Sage does nothing, yet nothing remains undone."
-Lao Tzu, Te Tao Ching