Editor content's stylesheet is removed from document after another editor's editable is reattached

[Piotrek Koszuliński]

1. Open widgetquote sample from #9764.
2. Switch between modes twice in first editor.
3. See that widget lost its styles in second (inline) editor.

Or:

1. Open datafiltering sample from master and find in dev tools last stylesheet (with data-cke-temp attr) in host page's head.
2. Switch between modes twice.
3. Stylesheet was removed...

Problem is somewhere here: ​https://github.com/ckeditor/ckeditor-dev/blob/master/core/editable.js#L681-L693

It seems that framed editor (wysiwygarea or sourcearea) does not increase stylesheet_ref, but it decreases it. Or that order of detach and new editable's setup is incorrect.