A few uses of error_set(ERROR_CLASS_GENERIC_ERROR) were missed in
c6bd8c70, or have snuck in since.  Nuke them.
Signed-off-by: NEric Blake <eblake@redhat.com>
Message-Id: <1447224690-9743-19-git-send-email-eblake@redhat.com>
Acked-by: NAndreas Färber <afaerber@suse.de>
[Indentation tidied up, commit message tweaked]
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>