core: Handle import status lines during keylist operation

* src/keylist.c (gpgme_op_keylist_from_data_start): Call
_gpgme_op_import_init_result.

This fixes a crash when importing keys from data. Initializing the
import result was missing for this keylist operation.

• Fixes-commit: f3ca57dfd7af19f9b2fd01616a81dc889707a4d3
• GnuPG-bug-id: T5951