openssh: Don't cache ac_cv_search_logout and ac_cv_search_openpty

These are in -lutil. Because the check for ac_cv_search_login is first -lutil gets already included when these tests are done. So the result is 'none required' which lets a subsequent build of dropbear fail.

git-svn-id: file:///var/svn/freetz/trunk@10640 149334a1-2f27-0410-a3b9-fc62619ac1e6