FreeBSD -- ssh-add does not honor per-hop destination constraints

Problem Description:
When using ssh-add(1) to add smartcard keys to ssh-agent(1) with
per-hop destination constraints, a logic error prevented the constraints
from being sent to the agent resulting in keys being added to the agent
without constraints.
Impact:
A malicious server could leverage the keys provided by a forwarded
agent that would normally not be allowed due to the logic error.