bsdbox: remove previously broken telnet(d) support

Support for telnet(d) was commented out some time ago. Remove because
telnetd is gone in main and this is unlikely to be fixed.

Reviewed by: imp, delphij, emaste
MFC after: 3 days
Differential Revision: https://reviews.freebsd.org/D36782

(cherry picked from commit c0f94ccbb241f530c9f89d5259efb695e4f6de95)