scd: Fail when no good algorithm attribute.

* scd/app-openpgp.c (parse_algorithm_attribute): Return the error.
(change_keyattr): Follow the change.
(app_select_openpgp): Handle the error of parse_algorithm_attribute.

Backport master commit of:
53eddf9b9ea01210f71b851b5cb92a5f1cdb6f7d

This change allows following invocation of app_select_openpgp, which
may work well (if the problem is device side for initial connection).

• GnuPG-bug-id: T5963
• Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>