Add a case of not freeing MBUF, when natpt_in4() returns IPPROTO_DONE.
Add a case of not freeing MBUF, when natpt_in4() returns IPPROTO_DONE.

MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame