OPAC Browse: Show authority tracings only when inter-authority links exist

OPAC Browse: Show authority tracings only when inter-authority links exist

This is something of a reversion to an earlier behavior.  Now we don't
display See Also tracings from an authority records linked to a bib
heading unless that authority record tracing is itself linked to another
authority record where the same tracing is a main entry.  Without that
authority-to-authority link, we can't say whether any bibs are
authority-linked to the "see also" term.

Unlike before, the tracings are available to the template even if a<->a
links aren't there, so a site could make a customization if they
preferred to see all tracings, linked or not.

Signed-off-by: Lebbeous Fogle-Weekley <lebbeous@esilibrary.com>