scd:piv: Fix authentication with Administration Key.

* scd/app-piv.c (auth_adm_key): Fix the value of the Response Tag.
(do_setattr): Fix the comment.

Cherry-pick master commit of:
7cfbf0dd72d8d5c14fbf19c13722d153bd1cbd70

• Reported-by: Heiko Schäfer <heiko@schaefer.name>
• Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>