MFC r325517, r325554

r325517:
ctl: Make max_luns and max_ports tunable variables instead of hardcoded
defines.

Reviewed by: trasz (earlier version), bapt (earlier version), bcr (manpages)
Sponsored by: Gandi.net
Differential Revision: https://reviews.freebsd.org/D12836

r325554:
ctl(4): Insert a new line after a sentence-ending full stop.

Reported by: bjk
Sponsored by: Gandi.net
X-MFC-With: r325517