scd: Fix closing reader and reeleasing context in PC/SC.
* scd/apdu.c (close_pcsc_reader): Unlock the reader_table_lock. (apdu_dev_list_finish): Release the context when no readers.
- Fixes-commit: 46d185f60397f68830bfdfb99627b29aea5016f1
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>