This allows the SSH_AUTH_SOCK environment variable to work inside of
su and agent forwarding to succeed.
Fixes#12467
Signed-off-by: Percy Wegmann <percy@tailscale.com>
This allows pam authentication to run for ssh sessions, triggering
automation like pam_mkhomedir.
Updates #11854
Signed-off-by: Percy Wegmann <percy@tailscale.com>