Do not corrupt the listen string when parsing it.

This fixes problem with ctld reload when it is configured to listen on two
portals with same IP, but different ports.

MFC after:	1 week


git-svn-id: svn+ssh://svn.freebsd.org/base/head@275452 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f