QbsProjectManager: Don't leak the "Reading project" progress bar.

If a qbs project gets closed (e.g. due to a session switch) while the
project is being loaded, the corresponding QFuture does not get deleted
and the progress bar will be around forever. This patch fixes that.
Note: The project resolving by qbs was already correctly canceled; this
is about the visual effect only.

Change-Id: If00aed949505088cfdb87d08e26f3b62ccea5fd1
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
Update qbs submodule.

To HEAD of the 1.3 branch.

Change-Id: Idf631edd93cf7dd0ac005634d2fcd2999f148099
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>