Make the new message format use the item field in resultsdb
When retrieving results for a koji_build greenwave is looking for the
fields: item and original_spec_nvr which was added at the time of the
Fedora Atomic CI pipeline where the nvr was later changed and would thus
no longer match what bodhi or greenwave would look for.
This means that for any results to be considered by greenwave, it needs
to have either fields.
With the new format, we know the nvr of the test result corresponds to
what bodhi/greenwave will be looking for, so we while could go with
original_spec_nvr it's not a default nor a common field unlike item.
So let's just record the nvr in the item field (in addition to the
nvr one) and this should make the result from the messages coming from
the new message format appear and matter for greenwave.
Signed-off-by: Pierre-Yves Chibon <pingou@pingoured.fr>