scd: Internal CCID driver: Fix a race condition on close.

* scd/ccid-driver.c (ccid_require_get_status): For VENDOR_SCM reader,
return 0 only at the initial call.
(bulk_in): Don't detect an error for VENDOR_SCM reader, just kicking
the loop, to invoke scd_update_reader_status_file, which calls
ccid_slot_status again.
(ccid_slot_status): Move the call of ccid_vendor_specific_setup to...
(ccid_get_atr): ... here.

For readers with interrupt transfer support, it is only intr_cb which
sets handle->powered_off to 1. Keeping this condition makes no race.
The function ccid_slot_status can also detect a communication error,
which causes apdu_close_reader (but not setting ->powered_off).

• GnuPG-bug-id: T5121
• Fixes-commit: 920f258eb6018ecec1d63bad6a0fb0772f72affa
• Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>