Fix unbound remote denial of service vulnerability.

Security:	FreeBSD-SA-14:30.unbound
Security:	CVE-2014-8602
Approved by:	so


git-svn-id: svn+ssh://svn.freebsd.org/base/releng/10.0@275854 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f