MFC: r286046

MFC: r286046
This patch fixes a problem where, if the NFSv4 server has a previous
unconfirmed clientid structure for the same client on the last hash list,
this old entry would not be removed/deleted. I do not think this bug would have
caused serious problems, since the new entry would have been before the old one
on the list. This old entry would have eventually been scavenged/removed.

git-svn-id: svn://svn.freebsd.org/base/stable/10@286164 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f