Do not count closing projects as open

[odeimaiz]

If the number of maximum open projects is set to one, after going back to the dashboard, users need to wait for the project to be closed before being able to open another one.

[sanderegg]

After some thoughts I think this might be an issue:

I guess we could say that a closing study does not count as an "open study" that is fair.
But what if it fails to stop? that means the resources are still in use and you can block the whole system. This is equivalent to this issue: #836
@odeimaiz @mguidon @pcrespov @matusdrobuliak66 @GitHK

I would propose to postpone this in favor of the state zip/unzip disabling and see from there if this is still a showstopper.

points:

1. It's annoying for the user to wait for the project to close, it can potentially fail.
2. removing the limit can potentially allow a user to open/close several projects and block the whole platform (i.e. other users) because it uses the resources for nothing (and closing can also potentially fail)
3. is s4l full limited to 1 project per user?
4. progress for closing the project?
5. disable zipping of state should improve speed when closing a project
6. have a separate counter for max allowed opened/closing projects

[odeimaiz]

I do believe that from a user's perspective this is a bug. Same goes for #846.