XWikiDocument context document switch shoud take into account secure doc (sdoc)

Right now when calling XWiki#getRenderedContent (which is supposed to be executed in the context of the document), if anything set a secure doc in the context before, the programing right will be checked on that secure doc instead of the content document (so really not the expected one).

Same issue but even worst with the hacky "lets temporary change the context document content author" that we can't easily work around (without some very crappy stuff like reloading the document from the DB). But this one should be fixed everywhere anyway (see XWIKI-11223 for example).