Item tags are not added to Exhibit tags facet

[ggeisler]

If I remember correctly, it used to be that when you added tags to exhibit items, each tag was immediately indexed to the Exhibit tags facet. This no longer seems to be the case. When I add a couple of tags to items, the Exhibit tags facet still shows no items.

I don't think this behavior was unique to Stanford exhibits, but if so, it doesn't seem to work there either.