[packagekit] Getting updates whilst updating system

[Richard Hughes]

If we are in the middle of a UpdateSystem call, and the user opens up
the update viewer, what are we supposed to do?

1. Queue the transaction, so the user just gets the pulsating bar for
~15 minutes
2. Return "No updates available"
3. Return the cached list of updates that we are installing

1 is what we do now, and is less than great. 3 would let the user queue
two update transactions, which probably isn't what we want.

Comments?

Richard.