hugolib: Fix "borrow content from another language" issue

hugolib: Fix "borrow content from another language" issue

If a content file contains shortcode(s), we have logic in place to re-render it per output format.

We also have logic in place that avoids making a copy of the content used for this process if we don't need it.

This was before this commit limited to server mode and if the page should be output to multiple formats.

But there is a third case: If a site (language) borrows and renders `.Content` from another language. This would, before this commit, behave oddly for content with shortcodes.

Fixes #4986