Link dialog history can list blog posts as pages instead

This is not always reproducible, but due to CONF-17972 the history in the link dialog can sometimes list blog posts as pages, and the links produced by it are therefore broken. They don't include the date and will render as links to create a page with the name of the blogpost.

This bug can be fixed by changing the PagePickerAction to pass a DefaultContentEntityManager into the UserHistoryHelper's constructor instead of a PageManger. That is, the following line (currently line 70) is broken.

            UserHistoryHelper userHistoryHelper = new UserHistoryHelper(getRemoteUser(), pageManager, permissionManager);

Some of the issues mentioned by CONF-17972 suggest that the bug may be reproducible by flushing the caches appropriately.