There are three things, which is done by current close_pcsc_reader.
- as a method for closing for a card reader
- releasing PC/SC context by pcsc_release_context
- nullify (clear) pcsc.rdrname fields.
pcsc.rdrname fields are set, to point reader name string which is gotten by pcsc_reader_list, and it is nullified by apdu_dev_list_finish (after freeing dl->table), even if there are still active/opened accesses to readers.