TPAC: Avoid showing URIs from 856 if we have OpenURL results

TPAC: Avoid showing URIs from 856 if we have OpenURL results

There is already a lot of logic to deduplicate OpenURL results versus
URIs in 856 fields, but in practice URIs in 856s tend to be subject to
bitrot, while SFX generally should be trustworthy. Thus, don't generate
electronic resources for 856s if we have OpenURL results.

Another optimization might be to hide the 856 results in case SFX is
wrong, then give users the ability to show them, but that might be
something we only want to enable in the staff client...

Signed-off-by: Dan Scott <dscott@laurentian.ca>