Fix second part of #5386.

Fix second part of #5386.

A \clearpage command issued right before \end{CJK} is recommended by the
package author to prevent any un-processed CJK chars outside the
\begin{CJK} and \end{CJK} scope. Otherwise, TOC, header, footer,
and may contain CJK chars but get processed outside the CJK environment scope.

Tha new dedicated export test fails without the fix.