scd: Backport two fixes from master.

scd: Backport two fixes from master.

* scd/app.c (app_new_register): Initialize by -1, so that it can detect
an error correctly when card reader can't power-on the card initially.
* scd/command.c (open_card_with_request): Release APP before the scan.

--
The first one-liner patch handles an erroneous card.

The second patch handles the case when we repeatedly do
signing/decrypting by a single session of scdaemon.

Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>
Gbp-Pq: Name 0028-scd-Backport-two-fixes-from-master.patch