sysutils/ttyd: Add -W flag and /usr/bin/login default program

-W             - flag is needed in order for clients to be able
                 to write into the terminal, otherwise it is read-only
/usr/bin/login - is needed for users to be logged in,
                 because this is what most users expect

PR:		289702
Approved by:	nc@FreeBSD.org (maintainer's timeout; 25 days)