Drop home-grown lookup code, which is a strange mix of a lookup table
and a list.  Use standard glib hash instead.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-id: 20180222070513.8740-3-kraxel@redhat.com