More clear scoping and interaction with running actions in
UmAccountDialog. In later 'enterprise login' patches we have long
running actions that's why this needs cleaning up.
In particular:
* Show errors as children of the dialog.
* Errors don't make the account dialog go away, user can correct
problems.
* Use more standard GAsyncResult style callbacks:
um_account_dialog_perform() um_account_dialog_finish()
* Disable controls while the operation is happening.
* Allow the user to cancel long actions in UmAccountDialog by
pressing the cancel button.
https://bugzilla.gnome.org/show_bug.cgi?id=677548
It's confusing to read; it reads as 'user manager'. Since this
is a GObject, just use self as customary.
Most of these lines change in later commits anyway, so this won't
really pollute the 'git blame'
https://bugzilla.gnome.org/show_bug.cgi?id=677548
