agent: Make sure to return success in ephemeral store mode.
* agent/genkey.c (store_key): Clear ERR on success.
This fixes a real problem which might let ephemeral store mode fail
randomly.
This is part of
(cherry picked from commit fdc5003956407da1984f40fc27115e4704587e15)
- GnuPG-bug-id: T7129
- Co-authored-by: Jakub Jelen <jjelen@redhat.com>