Fix optional arguments with description interactions

Fix optional arguments with description interactions

Ticket: CM-6659
Reviewed by: CCR-3203
Testing: See bug

If you have a cli like this:
"neighbor WORD interface {v6only}"

When in the cli you hit ? after entering v6only you get this:

tor-11(config-router)# neighbor swp1 interface v6only
% There is no matched command.
tor-11(config-router)# neighbor swp1 interface v6only

With this fix we now see:
tor-22(config-router)# neighbor swp1 interface v6only
<cr>
tor-22(config-router)# neighbor swp1 interface v6only

This behavior is now consistent with non-optional last
arguments.