ubuntuone-client blocks logout while syncing

This is by design, so people don't shut off their computers assuming everything has been backed up.

Then it seems an inadequate solution since it does not give the user the information they require to make an appropriate choice and does not indicate the consequences of choosing to shut down anyway.
- The sync might be downloading rather than uploading (backing up), and as a user, I might choose differently depending which is in progress.
- Even if it is still backing up my files, sometimes I'm in a hurry and I would like to take the risk, sometimes i'm not and Im prepared to wait. I'd like to know the consequence of my choice so I understand the risk.
- The message I see is that some process is running, I would prefer if when I try to shut down the message says "Ubuntu One is still syncing (followed by some measure of progress or what kind of operations are in progress) are you sure you want to interrupt it?"

This was discussed at UDS O and we're going to try to make the message more informative.

Marking as duplicate of a (later) bug that was already attached to the blueprint.