Set an empty keyring in rpmlib.get_rpm_header().
Set an empty keyring in rpmlib.get_rpm_header().

This may prevent a race-condition, because rpm opens rpmdb
to get keyring otherwise.

pombredanne/https-git.fedorahosted.org-git-kobo,pombredanne/https-git.fedorahosted.org-git-kobo,pombredanne/https-git.fedorahosted.org-git-kobo,release-engineering/kobo,release-engineering/kobo,release-engineering/kobo,pombredanne/https-git.fedorahosted.org-git-kobo,release-engineering/kobo