MFC r278354: Teach ctld(8) to control non-iSCSI CTL ports.

MFC r278354: Teach ctld(8) to control non-iSCSI CTL ports.

This change introduces new target option "port", that assigns current target
to specified CTL port.  On config application ctld(8) will apply LUN mapping
according to target configuration to specified port and bring the port up.
On shutdown cltd(8) will remove the mapping and put the port down.

This change allows to configure both iSCSI and FibreChannel targets in the
same configuration file in alike way.

Kernel side support was added earlier at r278037.

Relnotes:	yes
Sponsored by:	iXsystems, Inc.

git-svn-id: svn://svn.freebsd.org/base/stable/10@279055 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f