* agent/command-ssh.c (setup_ssh_env): Fix env setting.

[...]
(2) UPDATESTARTUPTTY doesn't work to switch TTY for pinentry for
    SSH.

[...]

Current implementation:

    In the function start_command_handler_ssh, the logic puts
    priority on ctrl->session_env which is initialized by
    agent_init_default_ctrl.  There are always GPG_TTY and TERM
    defined, because lines around 968 in gpg-agent.c, it says:

	/* Make sure that we have a default ttyname. */

    While UPDATESTARTUPTTY updates opt.startup_env, it doesn't
    affect at all.

Here is a patch to point the issue.  Tested and works for me.